By George Mullen

 

Desert tortoiseMost traditional methods for recovering gold from gravels require an ample supply of water. However, an old prospector’s adage has it that gold is where you find it. In the southwest, the “where” is all too frequently situated miles from even a trickle of water. Dry-washing of gold-bearing soil or gravel provides an effective solution to this dilemma.

Click here for a more thorough explanation of dry-washing techniques.

The Spaniards used a scheme similar to the winnowing of wheat from chaff and straw. Two men would grab the comers of a blanket, upon which a small quantity of classified gold-bearing material had been placed, and they repeatedly would toss it upward into the air. The wind would blow away the lighter fraction, and any gold and black sands, which are heavier, would fall back onto the blanket. Wool blankets worked best, because the static electrical charge generated by the wool tended to attract fine-sized gold on the blanket’s surface.

The modem prospector uses an efficient tool called a dry-washer to extract the ever-elusive gold particles from screened gravels or other material. Dry-washers can range in size and complexity from hand-shovel-fed models, to large machines serviced by wheeled or tracked front-end loaders.

All dry-washing machines require a low-pressure, high-volume source of air. At the low-cost end, this can be provided by a bellows which is linked to a hand-operated crank or motor-driven fly wheel. At the higher-cost end, the air source is typically provided by a gasoline engine-driven blower. The remaining components of a dry-washer combine to construct a sloped classification screen (or “grizzly”), which routes fine-sized material to a pneumatic sluice box, where a mechanically-modulated flow of air accomplishes the separation of gold from the lighter-weight material which contains no value.

Dry-washing for goldA dry-washer for small-scale prospecting might consist of a rectangular screen with 1/2 inch openings over a sloped trough. The screened material would pass from the lower-end of the trough to the head-end of a sloped riffle tray consisting of cotton fabric stretched over an inner frame. The tray includes sides to contain the flowing material, and its surface is interrupted by five crosswise riffles. Under the tray is a hollow box and the mechanism which modulates air flow through the tray at a rate of about 200 puffs per minute. The rate of air flow is designed to be sufficient to lift lighter material over the riffles, while the gold remains trapped. When everything is working right, the flow of material through the riffle tray resembles water flowing through a conventional sluice box.

My dry-washer was built from a plan published by Carl Fischer. It is mostly constructed of wood and is extremely portable. A small gasoline engine drives the air box via a belt and pulley speed reducer, producing the required 200 puffs of air per minute. The end result is an efficient separator which saves even the finest particles of gold. I have checked the tailings on numerous occasions and have yet to find any significant amount gold in them.

Prospecting for gold in the desert uses techniques similar to those that are used to locate placer gold on flowing streams or within old stream channels. You want to sample dry-washes on pediments to mountains, feeder-canyons in the mountains and ancient streambeds.

Another old prospector’s adage suggests that one should look for gold where it has been found before. This is still sound advice!

Very fine gold is abundant at many sites in the northwest, and the usual methods of final gold recovery do not always work very well. I have found that the screening and drying of dredge or high-banker concentrates, and then running them through my dry-washer, really works well. I use a metal detector to monitor both the feed and the tailings.

After processing pay-dirt material for about an hour, I suggest it is usually a good idea to clean-up the riffles to check your recovery. I use a plastic gold pan and small wash tub for the final clean-up and have operated all day on just a few gallons of water.

My wife, some friends and I operate suction dredges and high-bankers on the extensive New 49’er properties near Happy Camp, California during the summer months, where there is always an abundance of water. Our dry-washer allows us to remain active during the winter, usually around Quartzsite, Arizona. These gold prospecting and mining activities provide enjoyable activity, along with an extra source of income when we need it.

 
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By Dave McCracken

“Good organization always comes back to having some understanding in advance of what conditions you will encounter when it is time to complete the mission.”

 

Assuming legal access to the property has already been arranged, and company executives intend for us to proceed in this way, here are the primary objectives that we try and accomplish during the preliminary evaluation of a potential mining project:

1) Meet with company executives to gain an understanding of what the mining program is about, what the overall objectives are, the timing and the budget. Review the information which they have accumulated so far. Make plans for a departure-date.

2) Obtain the very best maps of the area that we can get our hands on.

3) Locate and study as much information as we can find concerning the mining history of the area, and the areas surrounding where the project will take place. Plot this information on the map. This includes finding out the type of mining methods that were being used, and what kinds of values have been recovered.

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4) Study background information about the geology, weather, culture, politics and economics of the area. This includes a look at the public information released by the U.S. State Department . Follow up with Internet research to see what others have to say about the people, events and mining activity within the area – and anything else of interest.

Is the political situation stable?

5) Establish a preliminary idea of how and where the potential project-area is located in relation to local communities, potential sources of supplies, emergency support, political structure and access. Bring together an early idea of what we want to see when we get there.

6) I always recommend that at least one representative (preferably one of the company directors) of the company accompany us through the full preliminary evaluation of the area where the potential project would take place. It is in the company’s best interest to have someone from existing management present to confirm our observations, and to help evaluate our conclusions.

7) Travel to the potential project area and:

A) Get a feel for the local politics in general, and in relation to the potential project. Will the locals ignore, support or object to the program? Are there pre-existing problems that will need to be fixed before beginning a sampling program? For example, the following video segment shows local campaigning on political issues within Madagascar that soon thereafter evolved into civil strife that disrupted all productive activity in the country for at least 6 months:

B) Find out the different ways of gaining access to the project site. Try and make contact with those people who would provide the transport service (if needed), and establish timing, cost and dependability. How can we make contact with them from the field? For example, the following video segments demonstrate boat transport services we needed to rely upon to support a dredging project in Cambodia :

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C) Locate sources of food, fuel, supplies and personnel to support the mining program. This would include any special needs, like local guides and boat operators out at the project-site. Establish the cost of things and dependability of the supply and/or services. Are there periodic shortages of supplies or services?

    

 

D) Locate the nearest place for competent medical assistance. Do they have any kind of emergency evacuation service? If not, perhaps they can provide a referral to the nearest large medical facility which does provide such a service. Develop a viable plan to provide competent medical care in the event that it may be needed, and how to mobilize the service from the field.

E) Establish support in local communities within the vicinity of where we would conduct the mining operations.

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F) Locate local miners and gain as much information as possible from them about what is being done, where and what results are being accomplished. Purchase samples of the values if possible and carefully log where they came from. Take a hard look at the gold, gemstones or other values being recovered. It is important to verify the activity and results. Look at how much value the locals are recovering, in relation to the volume of their production. Relate that back to what can be accomplished in production with suction dredging or other modern equipment.

    

 

    

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For example, the following video segment demonstrates a primitive hand-mining program that I stumbled upon along the border of western Viet Nam just a short while ago. These miners were breaking very small volumes of hard-rock ore free from the surrounding country rock with a hammer and chisel. The pieces of ore were being crushed by hand, and then surprising amounts of free gold were being panned in the river where we were sampling. While the amount of gold actually being recovered was not a lot, it was very rich compared to the very small amount of ore that was being processed by their primitive methods. Modern equipment and technology would turn this into an extremely valuable deposit:

The best local mining operations to observe are the ones that are actively processing the gravels within the waterway where our dredging would be done in a follow-up sampling operation.

For example, I captured the following video sequence where active gold mining was being done by local miners alongside and inside of the river where we were considering a suction dredge program in Africa several years ago. As the local miners were recovering a lot of gold in proportion to the volume of river gravels being processed, we decided that a follow-up dredge sampling program was justified:

G) Find out if there are special concerns about dangers in the water, within the surrounding area, sanitary problems, health concerns, or security worries. How will they be dealt with? Will there be any special needs for this?

For example, the following two video sequences were captured during a dredge sampling project that we completed in Cambodia several years ago at a time when there was an active (brutal) civil war in progress. The dangerous situation at the time required us to bring along a substantial contingent of security forces and also arm each of the specialists on our team:

Is the waterway full of big rocks that will require specialized equipment to winch out of our way?

    

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H) Free-dive in the river and/or probe from the surface to gain a good perception of what equipment will be needed to perform a preliminary sampling program. How deep and fast is the water? How deep is the streambed material to bedrock? Is there a lot of material too large to move by hand? Are submerged trees going to interfere with the sampling process? Are there excessive amounts of mud or sand that will overwhelm the recovery system?

It is often possible to bring up smaller-sized samples to pan from the bottom of the river, to get a better idea what a dredge sampling program will find.

I) Decide if special recovery methods will be required to perform a preliminary sampling program. If conditions present will mean that more portable equipment will be required, this may require a floating container be constructed to fully catch the samples, so they can be carefully processed on shore.

Or it may be that you can refit your sampling dredge so that it will effectively capture the fine gold from your samples. Here is a substantial explanation of the system which we have developed to effectively recover more fine gold on our conventional suction dredges. It combines two classification screens to more-effectively separate material-feed into three size-fractions, each which is directed into a different recovery system. The smallest gold particles (which are most difficult to recover) are directed into low-profile riffles along the bottom of the sluice box which have long been proven to be very effective at trapping fine gold.

  

J) Establish the potential for a commercial mining opportunity, based upon evaluation of pre-existing information and direct observation of ongoing local mining programs, along with whatever limited sampling can be accomplished using the resources that are immediately available.

K) Document all important details as well as possible by logging names, phone numbers (or email addresses) and locations of important contact persons, along with how much things will cost. Obtain digital images of everything important..

L) If appropriate, conceptualize a preliminary sampling program. This includes how the sampling program would be performed, supported, and how long it would take to complete. The concept should be consistent with the company objectives and budget.

8) Write a report which includes all of the important details of our findings. Include a photo-library with explanations for each image. The report should conclude with a recommendation. For example, Here is an example of the non-proprietary portion of a completed Report.

For a better understanding of why a preliminary evaluation is so important, I strongly encourage you to read about some of the sampling projects that we have accomplished in remote locations outside of America. The full list of the adventures I have written about can be found here . When reading these stories, it should become very clear to you that the potential success of any sampling program will largely come back to how well it is organized in advance. Good organization always comes back to having some understanding in advance of what conditions you will encounter when it is time to complete the mission.

 

 

Article & photos by David Lawler, Consulting’ Geologist

 

Placer deposits image 1Placer gold deposits represent the most attractive targets for small-scale miners and prospectors, since activities can be carried out with reasonably small costs, and encouraging prospecting results can be obtained rapidly. A small-scale miner has the opportunity to exploit small, rich accumulations of gold which larger-sized mining companies might pass by, due to reserve-size and overall ore-grade. In other words, because of the higher costs involved with a larger mining company, they will not be interested in some types of gold deposits which can be quite lucrative for a smaller-scale mining program.

Placer deposits have been exploited by man since early historic times and have remained an important source of gold on the world market into the 20th Century.

Placer deposits have yielded over 60% of the world’s gold production. Placer gold production in California alone during the height of the Gold Rush has been estimated at $81 million dollars. (Dollar-value in terms of $18/ounce in 1849, prior to 150 years of inflation).

While many texts and articles have been written on the subject of placer mining, the purpose of this article is to provide a brief overview of the subject and to introduce relevant facts which have practical application for the small-scale miner. The less common types of placers, e.g., Glacial, Aeolian, Bajada and beach placers will not be covered in this article.

Alluvial Placer Gold Deposits

Placer deposits image 2Definition: Alluvial deposits are the most common type of placer gold deposit. This category includes fluxial (river and stream) placers which formed in well-defined channels. It also includes “bench” or terrace deposits. These are older river or streambeds which formed on the elevated side slopes of drainage valleys. Both ancient (paleo placers) and modern deposits are included in this category and have produced significant amounts of gold.

Characteristics: Good sorting of sediment and gold particles by size and weight.

Sediments tend to be well transported, reflecting significant rounding or flattening of individual particles as a function of distance traveled from its source. The source of gold can either originate from a nearby lode deposit, generally leaving the gold’s surface with a rough texture; or the gold can have originated from distant sources, generally leaving it with smooth, flattened particles, flakes or nuggets.

Ancient Fluvial Placer Deposits

Placer deposits image 3Examples: (Ancient) Tertiary-age Ancestral, Yuba and Feather River systems, Sierra Nevada Mountains, California, Ancestral Klamath River system, Weaverville and Hornbrook basins Klamath Mountains, California. There are also widespread occurrences of other ancient gold-bearing channels in other western states in the U.S.

Prospecting Suggestions: Check areas where modem drainages (rivers, creeks, and gullies) have eroded ancient gold-bearing channel deposits. Many of these areas were worked by miners during the 19th Century, but there is still plenty of gold remaining for the modem-day small-scale miner.

For example, check side slopes of ridges which contain the ancient channel deposits, since these are areas that usually could not be exploited by hydraulic or ground-sluicing mine methods, due to lack of adequate water or water pressure. These virgin (unexploited) areas can produce eroded substantial pockets of placer gold.

Hydraulic Mine Pit areas often contain good prospects for small-scale mining. Check the exposed bedrock floor (representing the exhumed channel base) surfaces both for cracks and weathered cemented gravels. Gold may remain in small fractures and cracks in the bedrock. These areas can be particularly fruitful for electronic prospecting.

In addition, gold may be liberated from previously-cemented gravels after the long period of weathering on the pit floor. Check drain tunnels and tailraces that may have been cut into bedrock or the sides of the channel for several reasons: First, drain tunnels were driven through solid bedrock at the floor of a hydraulic pit to drain excess water and tailings from the working face of a mining excavation.

It is estimated that hydraulic mining methods lost between 30% – 50% of the gold that was liberated from the deposit. In addition, many of the drain tunnels were also used as the primary locations for the placement of elongated sluice box recovery systems. Thus, clean-ups were performed inside the tunnels. Although some of the drain tunnels have become choked with debris or collapsed from weathering, many still carry gold-bearing materials through the tunnels.

Testing and sampling of in-situ (in place) Tertiary gravel placers is one very proven method of locating valuable gold deposits for the serious small-scale mining operation today.

Modem Fluvial Placer Deposits

Placer deposits image 4Examples: Rivers and streams of the Sierra Nevada and Klamath Mountain areas in California.

Prospecting Suggestions: Prospect areas which are adjacent to known ancient channels or lode gold deposits, since modern river deposits will usually become more enriched close to those areas.

Gold-bearing stream and river channels must be examined and studied in detail in regard to their history, habit and special characteristics, in order to better-exploit the placers contained in them. Check available geologic maps of a particular river area or observe the different bedrock types which are present. This information will yield valuable clues to the location and manner of gold accumulation in various stretches of river.

Most modern-day small-scale prospectors are using suction dredges, sluicing gear, vack-mining equipment and/or gold pans to prospect for and develop these types of gold deposits.

Sample bench deposits adjacent to the active stream margin. Although these deposits are not as commonly reworked by stream processes, they often contain high concentrations of placer gold. Thick bench deposits containing gold-bearing material derived from hydraulic mines are still present along the margins of rivers and streams in the Sierra Nevada and Klamath Mountain regions of California.

Residual Placer Deposits

Placer deposits image 5Definition: Shallow mineral deposits forming directly from weathering and chemical disintegration of a gold-bearing quality vein near the surface. Residual deposits tend to be rich, but localized in occurrence, i.e., close to the vein or outcrop area. These are also termed “seam diggings” due to their occurrence in weathered gold-bearing quartz stringers contained in weathered schist and slate fracture-zones.

Examples: “Seam digging”s at Georgia Slide, Spanish Dry Diggings and French Hill areas, Georgetown Divide, El’Dorado County, California, Alleghany and Downieville districts, Sierra County, California, Humboldt Mountains area, Humboldt County, Nevada.

Prospecting Suggestions: Search in lode gold districts characterized by small high-grade gold-quartz vein pocket deposits. Focus your search into specific areas which are along the geologic trend of previously-exploited lode pocket deposits. Recent fires, landslides, or disturbance by logging operations are constantly exposing new virgin areas for prospecting.

Modern-day metal detectors may help in the exploration and exploitation of these deposits, due to shallow overburden and erratic distribution of the residual placer nuggets.

Eluvial (hill-slope) Placer Deposits

Placer deposits image 6Definition: Deposits representing the transitional stages between a residual and alluvial placer deposit (deposits which form in route between the lode erosion and drainage system). Residual gold tends to form accumulations in soil or colluvium by “creeping” along with material down a hill-slope.

Examples: Klamath Mountain region, California and Oregon.

Prospecting Suggestions: A metal detector can be the ideal tool for locating these deposits, since gold distribution tends to be spotty or erratic due to a poor degree of sorting and transportation. High-banking equipment can be very productive where an adequate water source is available nearby. Dry-washing equipment can be productive in places where there is no water available for processing. Mechanized earth-moving equipment is sometimes necessary to excavate thick eluvial deposits. In this case, small wash plants are being used to recover the gold.

Recommended Reading

Averill C. v: 1946, Placer Mining for Gold in California: California Div. Mines Bull. 135, 377 p.

Clark, B. 1965, Tertiary Channels: California: Div. Mines and Geology Mineral Inf. Service, Z 18

Clark, B. 1970, Gold Districts of California: California Division of Mines Bull. 193, 186 p.

Haley, C.S., 1923, Gold Placers of California: California Mining Bur. Bull. 92, 167 p. Jenkins, O.P., 1946, Geology of Placer Deposits, in Averill, C. Z Placer Mining for Gold in California: California Div. Mines Bull. 135 p, p. 147-216.

Lindgren, 1911, The Tertiary Gravels of the Sierra Nevada of California: U.S. Geol. Survey Prof. Paper 73, 226 p.

Whitney, J.D., 1880, The Auriferous Gravels of the Sierra Nevada of California: Harvard Coll. Mus. Comp. Zoology Mem. v. 6, no 1, 569p.

 
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By Dave McCracken

Any place along the gold path where there is protection from the main flow of water is a good location to sample for gold.

Dave Mack

 

Thorndike/Barnhart’s Advanced Dictionary defines “placer” as “A deposit of sand, gravel or earth in the bed of a stream containing particles of gold or other valuable mineral.” The word “geology” in the same dictionary is defined as “The features of the earth’s crust in a place or region, rocks or rock formations of a particular area.” So in putting these two words together, we have “placer geology” as the nature and features of the formation of deposits of gold and other valuable minerals within a streambed

The main factor causing gold to become deposited in the locations where it does is its superior weight over the majority of other materials which end up in a streambed. By superior weight, I mean that a piece of gold will be heavier than most any other material which displaces an equal amount of space or volume. For example, a large boulder will weigh more than a half-ounce gold nugget; but if you chip off a piece of the boulder which displaces the exact same volume or mass as the gold nugget, the nugget will weigh about six times more than the chip of rock.

As gold is eroded from its original lode, gravity, wind, water and the other forces of nature may move it away and downwards until it eventually arrives in a streambed.

Gold erodes from its natural lode and eventually 
is washed into an active waterway.

There are several different types of gold deposits that a prospector should know about, because they have different characteristics and are dealt with in different ways. They are as follows:

RESIDUAL DEPOSIT: A “residual deposit” consists of those pieces of the lode which have broken away from the outcropping of the vein due to chemical and physical weathering, but have not yet been moved or washed away from the near vicinity of the lode. A residual deposit usually lies directly at the site of its lode.

ELUVIAL DEPOSIT: An “eluvial deposit” is composed of those pieces of ore and free gold which have eroded from a lode and have been moved away by the forces of nature, but have not yet been washed into a streambed. The fragments of an eluvial deposit are often spread out thinly down along the mountainside below the original lode. Usually, the various forces of nature cause an eluvial deposit to spread out more as its segments are washed further away from the lode deposit. Individual pieces of an eluvial deposit are popularly known as “float.”

An eluvial deposit contains those pieces of ore that have been swept
away from the lode which have not yet been deposited by running water.

BENCH DEPOSIT: (Also “terrace deposit”) Once gold reaches a streambed, it will be deposited in common ways by the effects of running water. Most of the remainder of this article will cover these ways. During an extended period of time, a stream of water will to cut deeper into the earth. This leaves portions of the older sections of streambed high and dry. Old streambeds which now rest above the present streams of water are referred to as “benches.” Accumulations of gold and other valuable minerals contained in an old, high streambed are called “bench deposits.”

An eluvial deposit might be swept down to rest on top of an old streambed (bench), but it will still remain as an eluvial deposit until it is washed into a stream of water. A bench placer deposit contains the gold deposited within that streambed before it was left high and dry.

Many benches are lying close to the present streams of water, and are actually the remains of the present stream as it ran a very long time ago.

Some dry streambeds (benches) are situated far away from any present stream of water. These are sometimes the remains of ancient rivers which ran before the present river systems were formed. Ancient stream benches are sometimes on top of mountains, far out into the deserts, or can be found near some of today’s streams and rivers. Ancient streambeds, wherever found, can contain rich deposits of gold.

Most surface placer gold mining operations today direct their activities at bench deposits. The reason for this is that the presence of an old streambed is evidence that it has never been mined before. Any gold once deposited there will still be in place.

STREAM PLACER: In order to discuss what happens to gold when it enters a stream of water, it is first necessary to understand the two terms: “bedrock” and “sediments.” Many millions of years ago, when the outer perimeter of the earth cooled, it hardened into a solid rock surface–called “bedrock” (or “country rock” when discussing the subject of lodes). All of the loose dirt, rocks, sand, gravel and boulders which lie on top of the earth’s outer hardrock surface (bedrock) are called “sediments.” In some areas, the sedimentary material lays hundreds of feet deep. In other areas, especially in mountainous country and at the seashore, the earth’s outer crust (bedrock) is completely exposed. Bedrock can usually be observed by driving down any highway and looking at where cuts have been made through the hard rock in order to make the highway straight and level.

Streambeds are composed of rocks, sand, gravel, clay and boulders (sediments) and always form on top of the bedrock foundation (although they can be later covered up by volcanic activity). Bedrock and country rock are the same thing.

Streambeds are composed of sediments which lie on top of bedrock.

The following video segment will allow you a visual demonstration of these very important points:

A large storm in mountainous country will cause the streams and rivers within the area to run deeper and faster than they normally do. This additional volume of water increases the amount of force and turbulence that flows over the top of the streambeds lying at the bottom of these waterways. Sometimes, in a very large storm, the increased force of water is enough to sweep the entire streambed down the surface of its underlying bedrock foundation. It is this action which causes a streambed to cut deeper into the earth over an extended period of time. A storm of this magnitude can also erode a significant amount of new gold into the streambeds where it will mix with the other materials.

Gold, being heavier than the other materials which are being swept downstream during a large storm, will work its way quickly to the bottom of these materials. The reason for this is that gold has a much higher specific gravity than the other streambed materials and so will exert a downward force against them. As the streambed is being vibrated and tossed around and pushed along by the tremendous torrent of water caused by the storm, gold will penetrate downward through the other materials until it reaches something which will stop its descent-like bedrock. This very important principle is demonstrated by the following video segment:

With the exception of the finer-sized pieces, it takes a lot of force to move gold. Since gold is about 6 times heavier than the average of other materials which commonly make up a streambed, it takes a lot more force to move gold down along the bedrock than it does to move the other streambed materials.

So there is the possibility of having enough force in a section of river because of a storm to sweep part of the streambed away, yet perhaps not enough force to move much of the gold lying on bedrock.

When there is enough force to move gold along the bottom of a riverbed, that gold can then become deposited in a new location wherever the force of the flow is lessened at the time of the storm.

Bedrock irregularities at the bottom of a streambed play a large role in determining where gold will become trapped. A crack or crevice along the bedrock surface is one good example of a bedrock gold trap.

Streambeds are composed of sediments which lie on top of bedrock.

Many bedrock gold traps are situated so that the main force of water, being enough to move gold, will sweep the traps clean of lighter streambed materials. This leaves a hole for the gold to drop into and become shielded from the main force of water and material which is moving across the bedrock. And there the gold will remain until some fluke of turbulence boils it out of the hole and back into the main force of water again, where it can then become trapped in some other such hole, and so on. The following video segment further demonstrates these important points:

Some types of bedrock are very rough and irregular, which allows for many, many gold traps along its surface.

Some bedrock surfaces are very rough and
irregular–which allows for many gold traps.

How well a crevice will trap gold depends greatly upon the shape of the crevice itself and its direction in relation to the flow of water during a flood storm. Crevices extending out horizontally into a riverbed can be very effective gold-catchers, because the force of water can be enough to keep the upper part of the crevice clean of material, yet the shape and depth of the crevice may prevent gold from being swept or boiled out once it is inside.

Crevices running lengthwise with the flow of the stream or in a diagonal direction across the bed can be good gold traps or poor ones, depending upon the shape of the crevice and the set of circumstances covering each separate situation. For the most part, water force can get into a lengthwise crevice and prevent a great deal of gold from being trapped inside. However, this mostly depends upon the characteristics of the bedrock surface, and there are so many possible variables that it is no use trying to cover them all-such as the possibility of a large rock becoming lodged inside a lengthwise crevice, making its entire length a gold trap of bonanza dimensions. There is really no need to say much more about lengthwise-type crevices. Because if you are mining along and uncover one, you are going to clean it out to see what lies inside, anyway.

Potholes in the bedrock foundation of a streambed have a tendency to trap gold very well. These usually occur where the bedrock surface is deteriorating and some portions are coming apart faster than others, leaving holes which gold can drop into and thereafter be protected from the main force of water.

Bedrock dikes (upcroppings of a harder type of bedrock) protruding up through the floor of a streambed can make excellent gold traps in different ways, depending upon the direction of the dike. For example, if a dike protrudes up through the floor of a streambed and is slanted in a downstream direction, gold will usually become trapped behind the dike where it becomes shielded from the main force of the flow. A dike slanting in an upstream direction is more likely to trap gold in a little pocket just up in front.

Hairline cracks in the bedrock surface of a streambed often contain surprising amounts of gold. Sometimes you can take out pieces of gold that seem to be too large for the cracks that you find them inside of, and it leaves you wondering how they got there. Once in a while, a hairline crack will open up into a space which holds a nice little pocket of gold.

Hairline cracks can hold plenty of gold, and sometimes open up into small pockets.

How smooth the bedrock surface is has a great deal to do with how well its various irregularities will catch gold. Some types of bedrock, like granite for example, are extremely hard and tend to become pounded into a smooth and polished surface. Polished bedrock surfaces like this generally do not trap particles of gold nearly as well as the rough types of bedrock surfaces do. Also, polished bedrock, which sometimes contains large, deep “boil holes” (holes which have been bored into the bedrock by enormous amounts of water turbulence), is often an indication of too much turbulent water force to allow very much gold to settle there during flood storms.

Rougher types of bedrock, often being full of both large and small irregularities, have the kind of surface where many paying placer deposits are found. This kind of bedrock can be very hard and still maintain its roughness. Or it can be semi-decomposed. Either way, it can trap gold very well.

Rough bedrock surfaces tend to trap gold very well.

Basically, anywhere rough bedrock is situated so that its irregularities can slacken the force of water, in a location where gold will travel, is a likely place to find gold trapped.

Obstructions in a streambed can also cause the flow of water to slow down and can be the cause of a gold deposit, sometimes in front and sometimes to the rear of the obstruction. An outcropping of bedrock jutting out into a stream or river from one side can trap gold in various ways, depending upon the shape of the outcropping and the direction it protrudes into the stream. An outcropping extending out into the river in an upstream direction is most likely to trap gold in front of the outcropping where there is a lull in the water force. A gold deposit is more likely to be found on the downstream side of an outcropping which juts out into the river in a downstream direction, because that is where the force of the flow lets up.

LARGER GOLD TRAPS: PAY-STREAK AREAS

One of the most common locations within a stream or river to find a gold deposit is where the bedrock drops off suddenly to form a deep-water pool. Any place where a fixed volume of water suddenly flows into a much larger volume of water is a place where the flow may slow down. Wherever the flow of water in a streambed slows down during a major flood storm is a good place for gold to be dropped. And so it is not uncommon to find a sizable gold deposit in a streambed where there is a sudden drop-off into deeper water.

Any sudden drop-off into a deeper and larger volume of water is a likely spot to look for a sizable deposit of gold.

A waterfall is the extreme example of a sudden bedrock drop-off and can sometimes have a large deposit of gold at its base-but not always. Sometimes the water will plunge down into the hole of the falls and create so much turbulence that gold dropped into the hole during a storm can become ground up or boiled out. This is also potentially true of any other lesser sudden drop-off locations inside of a waterway.

On the other hand, sometimes large boulders can become trapped at the base of a falls and protect the gold from becoming ground up or boiled out by the turbulence. In this case the falls can become a bonanza.

In some waterfalls (or lesser sudden drop-off locations) the gold that has been boiled out will drop just outside of the hole, where the force of water has not yet had enough runway to pick up speed again-at least not enough to carry off much of the gold which arrives there.

Waterfalls are usually the territory of the suction dredger, because this type of gold trap usually deposits the gold underwater. Yet, this is not always the case. Sometimes during the low water periods of the year, some of the area below a falls can be exposed. There might be only a small amount of streambed to move in order to reach bedrock-where most of the gold is likely to be. The only dependable way to determine if gold will be present below a falls, or any other sudden drop-off location in a waterway, is to sample around and find out. Usually this is rather easy (unless you run into huge boulders); because if the area has been boiled out and swept clean of gold, often the bedrock will be exposed or have a layer of light sand and gravel on top. Again, this is not always true. Each falls has its own individual set of circumstances.

Another common location where a sizable gold deposit might be found is where the layout of the countryside causes the stream to run downhill at a rather steep grade for some distance and then suddenly it levels off. It is just below where the slope of the streambed levels off that the water flow will suddenly slow down during a major flood storm. This is where you are likely to find a concentration of gold. Areas like this are known for their very large deposits (pay-streaks).

The area just below where a streambed’s slope lessens often contains a good-sized gold deposit.

Boulders are another type of obstruction which can be in a riverbed and cause gold to drop out of a fast flow of water. Boulders are similar to gold in that the larger they are, the more water force it takes to move them. Sometimes during a storm, the force of water can pick up enough to sweep large amounts of streambed material and gold down across the bedrock. When this happens, the force may or may not be great enough to move the large boulders. A large boulder which is at rest in a stream, while a torrent of water and material is being swept past it during a large storm, will slow down the flow of the stream just in front, below and somewhere behind the boulder. This being the case, if the storm’s torrent happens to sweep gold near the boulder, some of the gold may concentrate where the slackening of current is at the time of the storm.

A boulder at rest in a streambed during a large storm might trap gold wherever it slows down the water force.

One thing to know about boulders is that they do not always have gold trapped around them. Whether or not a specific boulder will have a deposit of gold along with it depends greatly upon whether or not that boulder is in the direct path the gold took when it traveled through that particular section of streambed during earlier major flood storm periods.

THE PATH THAT GOLD FOLLOWS

Because of its weight, gold tends to travel down along a streambed taking the path of least resistance. For the most part, this seems to be the shortest route possible between major bends in the stream.

Gold tends to follow the shortest route possible between any major changes in the direction of the stream or river.

Take note that the route the gold is taking rounds each curve towards the inside of the bends in the river. While this might not be the route gold always takes in a streambed, it is true that when it comes to curves, the majority of gold deposits are found towards the inside of bends. In comparison, very few are found towards the outside. Centrifugal force causes a much greater energy of flow to the outside of the bend. This creates less force towards the inside, which allows for gold to drop there.

 

It is important for you as a prospector to grasp the concept that under most conditions, gold tends to travel the shortest distance between the bends of a stream or river, and it also seems to deposit along the inside of the bends. Your best bet in prospecting is to direct your sampling activities towards areas which lie in the path that gold would most likely follow in its route downstream within the waterway. This requires an understanding of what effects the various changes in bedrock and the numerous obstructions will have on changing and directing the path of gold as it is pushed downstream during extreme high water periods. For example, if you are sampling for concentrations of gold around and behind boulders, you are better off to begin with the boulders lying in the path that gold would most likely take. This is likely to be more productive than just sampling boulders randomly in the streambed, no matter where they are located.

WHERE THE STREAMBED WIDENS

Another situation within a stream or river where there is often a sizable concentration of gold (pay-streak) is where the stream runs narrow or at a certain general width for some distance and then suddenly opens up into a wider portion of streambed. Where the streambed widens, the water flow will generally slow down, because the streambed allows for a larger volume of water in such a location-especially during extreme high water periods. Where water force slows down is a likely place for gold to drop.

Anywhere that a streambed suddenly widens enough to slow the force of the
stream during high water periods is a likely place to find a deposit of gold.

Notice that some boulders will also drop where the water force is suddenly slowed down. Boulders are similar to gold in that it takes a tremendous amount of force to push them along. Wherever that force lets up enough, the boulders will drop. So boulders are often found in the same areas where large amounts of gold are deposited. But gold is not always found where boulders are dropped. This is because there are so many boulders within the waterway, and the majority of them probably do not continuously follow the same route that gold generally takes. Nevertheless, it is well to take note that those places where boulders do get hung up, which are on the same route that gold follows down the waterway, are generally good places to direct some of your sampling activities.

ANCIENT RIVERS

About two million years ago, towards the end of the Tertiary geological time period, the mountain systems in the western United States underwent a tremendous amount of faulting and twisting, changing the character of the mountains into much of how they look today. It was during the same period when the present drainage system of streams, creeks and rivers were formed, which runs pretty-much in a westerly direction.

Prior to that, there was a vastly different river system, which generally ran in a southerly direction. These were the old streambeds which ran throughout much of the Tertiary geologic time period, and so are called “tertiary channels” or“ancient rivers.” The ancient rivers ran for millions of years, during which time an enormous amount of erosion took place, washing very substantial amounts of gold into the rivers from the exposed rich lode deposits.

The major changes occurring towards the end of that period, which rearranged the mountains and formed the present drainage systems, left portions of the ancient channels strewn about. Some portions were placed on top of the present mountains. Some were left out in the desert areas. And some portions were left close to, and crossed by, the present drainage system.

Some geologists have argued that most of the gold in today’s river systems is not gold that has eroded more recently from lode deposits, but gold that was eroded out of the old ancient riverbeds where they have been crossed by the present river systems.

The ancient channels, where they have been discovered and mined, have often proven to be extremely rich in gold deposits. In fact, many of the richest bonanzas that have been found in today’s river systems have been discovered directly downstream from where they have crossed the ancient streambed gravels. Other areas which have proven to be very rich in today’s river systems have been found close to the old channels, where a few million years of erosion have caused some of the channel and its gold to be eroded into the present streambeds.

Ancient channels (benches) are well known for their very rich bottom stratum. This stratum is sometimes of a deep blue color; and indeed the rich blue color, when encountered, is one of the most certain indicators that ancient gravels are present. This bottom stratum of the ancient gravels was referred to by the old-timers as the “blue lead”, probably because they followed its path all over the west wherever it led them.

Ancient blue gravels usually oxidize and turn a rusty reddish brown color after being dug up and exposed to the atmosphere. They can be very hard and compacted, but are not always that way.

Running into blue gravel at the bottom of a streambed does not necessarily mean that you have located an ancient channel. But it is possible that you have located some ancient gravel (deposited there from somewhere else) which might have a rich pay-streak associated with them.

Most of the high benches that you will find up alongside today’s rivers and streams, and sometimes a fair distance away, but which travel generally in the same direction, are not Tertiary channels. They are more likely the earlier remnants of the present rivers and streams. These old streambeds are referred to by geologists as “Pleistocene channels.” They were formed and ran during the time period between 10,000 years ago and about a million and a half years ago — which was the earlier part of the Quaternary Period, known as the Pleistocene epoch. Some high benches that rest alongside the present streams and rivers were formed since the passing of the Pleistocene epoch. These are referred to as “Recent benches,” having been formed during the “Recent epoch” (present epoch).

Some of these benches, either Pleistocene or Recent, are quite extensive in size. Dry streambeds are scattered about all over gold country, some which have already been mined, but many are still untouched.

Usually, all that is left of a bench after it has been mined are rock piles. Notice in the picture that part of the non-mined streambed is in the background, behind the trees.

Usually all that is left of a high bench after it has been mined are piles of the larger-sized streambed rocks and boulders.

Most of the hydraulic mining operations which operated during the early to mid-1900’s were directed at high benches.“Hydraulic mining” was done by directing a large volume of water, under great pressure, at a streambed to erode its gravels out of the bed and through recovery systems, where the gold would be trapped.

A hydraulic mining operation. Photo courtesy of Siskiyou County Historical Museum.

So some bench gravels have been mined, but many of them still remain intact. While the Pleistocene and Recent benches are generally not as rich in gold content as were the Tertiary’s, it still remains true that an enormous amount of gold washed down into these old channels when they were active. They are pretty darn rich in some areas, and pay rather consistently in others. Also, any and all gold that has ever washed down into an old bench which has yet to be mined still remains there today.

FLOOD GOLD

A large percentage of the gold found in today’s creeks and rivers has been washed down into them out of the higher bench deposits by the erosive effects of storms and time. A certain amount of gold is being washed downstream in any river located in gold country at all times, even if only microscopic in size.

The larger a piece of gold is, the more water force that it takes to move it downstream in a riverbed. The amount of water force it takes to move a significant amount of gold in a riverbed is usually enough force to also move the streambed, too. This would allow the gold to work its way quickly down to the bedrock, where it can become trapped in the various irregularities.

Some streambeds contain a high mineral content and grow very hard after being in place for an extended period of time.

Sometimes a storm will have enough force to move large amounts of gold, but will only move a portion of the entire streambed, leaving a lower stratum in place in some locations. When this happens, the gold moving along at the bottom of the flooding layer can become trapped by the irregularities of the unmoving (“false bedrock”) streambed layer lying underneath. The rocks in a stable lower stratum can act as natural gold traps.

Flood gold is that gold which rests inside and at the bottom of a flooding layer.

Different streambed layers, caused by major flood storms, are referred to as “flood layers.” The flood layers within a streambed, if present, are easily distinguished because they are usually of a different color, consistency and hardness from the other layers of material within the streambed. That gold found at the bottom of or throughout a flood layer is often referred to as “flood gold.” Sometimes, the bottom of a flood layer will contain substantially more gold than is present on bedrock. Sometimes, when more than one flood layer is present in a streambed, there will be more than one layer of flood gold present, too.

The larger that a piece of gold is, the faster it will work its way down towards the bottom of a layer of material as it is being washed downstream during a storm. Finer-sized pieces of gold might not work their way down through a flood layer at all, but might remain disbursed up in the material.

So you can run across a flood layer which has a line of the heavier pieces of gold along its bottom edge, or a flood layer which contains a large amount of fine gold dispersed throughout the entire layer. You can also run across a flood layer which contains a lot of fine gold dispersed throughout, in addition to a line of heavier gold along the bottom edge.

Not all flood layers contain gold in paying quantities for a small-scale mining program. But in gold country, all flood layers do seem to contain gold in some quantity, even if only microscopic in size.

GRAVEL BAR PLACERS

Gravel bars located in streambeds flowing through gold country, especially the ones located towards the inside of bends, tend to collect a lot of flood gold, and sometimes in paying quantities even for the smaller-sized operations. The flood gold in bar placers is sometimes consistently distributed throughout the entire gravel bar. Sometimes the lower-end of a gravel bar is not as rich as the head of the bar, but the gold there can be more uniformly dispersed throughout the material.

FALSE BEDROCK

Once in a while a prospector will uncover an extremely hard layer of streambed material located just above the bedrock and mistake the layer for bedrock because of its hardness. A hard layer is often referred to as “false bedrock.” Such a layer can consist of streambed material, or of volcanic flows which have laid down and hardened on top of bedrock, or it can consist of any kind of mineral deposit which has hardened over time on top of the true bedrock.

There can be a good-paying gold deposit underneath a false bedrock layer. But when there is, it is usually rather difficult to get at.

Actually, for the purpose of sampling, the top of every different storm layer within a streambed should be considered a“false bedrock” and can be a surface-area for gold to become trapped out of the flood layer which laid down on top.

 
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By Dave McCracken

Under many circumstances, it is wise to first verify that a viable deposit exists on a property before a substantial investment is made into production equipment.

Dave Mack

 

How to outfit a suction dredging project, to a large degree, comes back to how you would answer the following questions:

1) What am I trying to accomplish; (sampling, production, or both)?

2) Where?

3) In what period of time?

4) How much of a budget is available for acquisition of equipment and for operational start-up costs?

A gold (and/or gemstone) mining project basically should to be looked at in two separate steps: First you sample to locate a viable deposit. Then you launch into a production program to recover the gold or other valuable minerals from the deposit. Generally, the idea is to minimize investment into a particular mining property until a viable deposit has been located and verified.

Production-equipment is commonly larger and is more expensive to purchase and move around. The logistical infrastructure to support a production operation is usually more substantial and costly than what would normally be required to just go in somewhere for a short sampling program. . So generally-speaking, a production operation costs more to set up and involves more gear and supplies to move around and put into place. Therefore, under many circumstances, it is wise to first verify that a viable deposit exists on a property before a substantial investment is made into production equipment. The idea behind sampling is to minimize risk.

Prospecting Equipment & Supplies

The following video sequence will provide you with a visual demonstration of this very important point:

A typical camp to support a preliminary sampling operation usually would involve just the basic necessities.

The answers to “Where?” and “For how long?” also impact upon your decision about what kind of gear to buy. For example, if you are not tied to just one mining property, and you are prepared to launch a sampling program onto different properties until you find what you are looking for, then it would be a good idea to invest in good sampling equipment that is portable enough to move around the properties which are available to you. In this case, the capital expenditure is not tied to a single property, but rather into a portable sampling infrastructure that can be used for an extended period of time in many different places.

While sampling-gear is more portable, the smaller the size of a dredge, the less volume of streambed material it will process (in the same experienced hands), and the less-deep it will effectively excavate a sample into the streambed. Therefore, you trade-off productive effectiveness and the capability to make meaningful, deeper samples as you reduce dredge-size and gain in portability.

Two Pro-Mack 5-inch dredges were used to find rich deposits on this river in Cambodia, before a 10-inch production dredge was brought on line.

As an example of this, a 4-inch dredge can effectively sample down to around 4-feet deep in hard-packed streambed material). A 5-inch dredge can excavate about twice the volume of a 4-inch dredge down to around 5-feet of material. But the bulk of gear to move around is about twice as much.

A 6-inch dredge can excavate about twice the volume of a 5-inch dredge down to around 6-feet of hard-packed streambed. But the bulk of gear to move around is about twice as much.

An 8-inch dredge can excavate about twice the volume of a 6-inch dredge down to around 8-feet of material. But the bulk of gear to move around is about twice as much.

Here follows a video segment of a typical commercial dredge operating on the Klamath River in Northern California:

Ten-inch Pro-Mack dredge operating on New 49’er properties in Northern California.

A 10-inch dredge can excavate about twice the volume of an 8-inch dredge down to around 10-feet of material. But the bulk of gear to move around is about twice as much. By now, we are talking about a pretty substantial platform. But it still remains portable enough to place inside of an ocean shipping container, and can be towed around on wheels behind a small truck. For example, watch how this recovery platform for a 10-inch production dredge can be moved around by a normal-sized truck. This particular platform was built to ship overseas inside of an ocean shipping container:

These are just guidelines, because conditions change from one location to the next. It does not mean you cannot dredge deeper into the streambed using smaller-sized dredges. You can! But it generally does mean that the deeper you go beyond these guidelines, the less effectively your time will be invested. This is mostly a matter of over-sized rock management. All rocks that are larger than the intake-size of the dredge’s suction nozzle must be moved out of the way by hand. When dredging in an average hard-packed streambed, at the point where an experienced operator gets down through 5-feet of material using a 5-inch dredge, he has so many rocks to get out of the dredge hole that he is lucky to spend half his dredging-time operating the suction nozzle!

Bigger dredges get more accomplished primarily because they will suck up larger-sized rocks.

Under most circumstances, there are a proportionate greater number of smaller-sized rocks in a hard-packed streambed, than larger-sized rocks. So this is really a discussion about effective time-management. Since a larger dredge will suck up a larger rock, it means the operator will not have to move smaller-sized rocks from the excavation by hand. So he or she will spend his time moving even larger rocks out of his way, of which there are proportionally-fewer. This means he will get more done faster, and be able to dredge deeper into the material, before he reaches the point that there are just too many rocks to move out of the way.

Using a 5-inch dredge will mean having to move many, many more rocks by hand that would more-easily be sucked up the nozzle of a larger dredge.

This important reality cannot be overcome by positive thinking or an abundance of enthusiasm (as important as these are to have). We are talking here about the physical reality of how an excavation is accomplished. The size of the dredge-nozzle determines what size of rock can be sucked up (which is fast and easy), and what must be moved out of the hole by hand (which takes more time and effort).

The following video sequence demonstrates this very important point, and also explains why you must be very careful about projecting the true volume capability of different-sized dredges during feasibility planning:

By the way, when conditions allow for it and you want to increase the productive capacity of your equipment, you can also organize two or three separate teams to take shifts using the same production equipment. As demonstrated in the following video sequence, lights can even be set up to do a night shift:

So when deciding what to acquire for sampling or production equipment, it is necessary to balance the desire to get more productive activity accomplished (bigger dredge), with the necessity to remain portable (not so big that you cannot move it around to find what you are looking for). This must be decided on a case-by-case basis.

Here is my advice: Go as big as you are able to without forfeiting the portability that is required for your particular situation. I suggest these important decisions can only be wisely made after at least a preliminary evaluation of the project-area is completed.

Once you have proven-out your deposit(s) by sampling, you can feel more comfortable investing in production equipment and support-infrastructure to develop the project. In that case, bigger is not always better. Sometimes it is. A lot will depend upon the depth of water and streambed where you will be dredging. For example, a 10-inch dredge might not be as productive as a 6-inch dredge in a shallow-water and shallow-streambed area where a larger dredge cannot be floated around easily.

Another example is where shallow streambed material is made up largely of boulders that must be winched out of the way. In this case, some of your money might be better invested into a good mechanical or hydraulic winch, rather than a larger-sized dredge.

A well-done preliminary sampling program should result in a good production plan, based upon what type of equipment will be required to obtain optimum production under the conditions which exist where the gold deposit is located.

I am not going to discuss sampling, production or recovery systems here, because they have been covered in other articles. But since the type of equipment you should acquire is directly related to these subjects, I suggest it is a good idea to review that material very closely.

Some dredges are made to operate from the surface with the use of an automated cutter-head device at the nozzle. These are generally ineffective in hard-packed streambeds that are mostly made up of oversized rocks.

Some dredges are available with hydraulic-powered cutter-heads to help with the excavation. These are mechanical devices that help feed material evenly into the nozzle. They are most productive in doing channel-work in harbors or making navigation channels deeper or wider. Hard-packed streambeds which are made up mainly of oversized rocks and boulders will usually destroy a cutter-head device in short order.

Here follows the normal steps in the development of a mining program:

1) Preliminary evaluation: This is where you take a hard look at the available information about a potential project. Then you go out and have a direct look at the specific location(s) and surrounding area. You are looking at the potential for commercial gold (and/or gemstone) deposits. You are also looking at what it would take to accomplish a preliminary sampling program, based upon all of the information and observation you can bring together. A preliminary evaluation will often result in a preliminary sampling plan.

2) Sampling Program: Depending upon what the objectives are, sometimes sampling is accomplished in several stages. Generally, the purpose of a sampling program is to locate and verify the existence of a commercial deposit that is valuable enough to justify a production operation. Sampling should work out the recovery method upon which the deposit may be developed efficiently. A sampling program can evolve into feasibility planning to develop a mineral deposit.


3) Production Operation: Is full or partial development of the deposit.

While there can be some overlap, equipment needs are usually different in each phase of a mining program.

While each project is different, during a preliminary evaluation, I personally always at least bring along a face mask (so I can have a look at the underwater environment where we would sample), a gold pan and classification screen, zip-lock sample bags and marker pen, map, GPS, camera equipment, local money in small denominations (to buy mineral samples from local miners), a dozen bright-colored ball-caps (gifts for local miners), a bottle or two of whiskey (gift for the village chief in non-Muslim communities), and the other basic things I will need to visit that particular environment.

A sampling program will basically require the same things as will be required in a full production operation, but usually on a smaller and more portable scale. Here follows a basic outfitting list:

Dredging Equipment:
Dredge
Boat (and motor?) and ores
Winching gear and rigging?
Pry-bars
Rope (floating)
Fuel containers
Complete set of tools needed to service the gear

Diving Equipment:
Face mask
Air reserve tank and fittings
Air line(s) & regulator(s)
Wet-suit?
Weight belt & weights
Protective foot ware (steel tips?)
Rubber work gloves (bring spares?)

Clean-up Gear:
Wash tubs
Classification screens
5-gallon buckets
Scraping tool and/or hand scoop
Final concentrating equipment?
Gold pans
Steel finishing pans
Magnet
Portable gas stove
Weight scale
Zip-lock sample bags and marker pen

Support Gear:
Vehicle-support?
Shelter
Cooking & eating utensils
Wash tub for kitchen
Cook stove
Toilet facilities?
Portable chairs & table
Medical kit
Waterproof bag(s)
Ear infection preventative
Maps, GPS and camera equipment
Electric generator?
Camp lights
Paper and pens
Communication equipment?
Flashlights & batteries
Knife
Firearm?

Supplies:
Drinking water and/or filters
Food supplies and containers
Fuel & motor-oil for all motors
Dish washing detergent
Chlorine for sanitizing cleaning water
Laundry wash tub and soap
Hand-wash soap
Tissue paper
Cook stove fuel or canisters
Duct tape
Nylon line (plenty)
Plastic trash bags
Zip-lock bags & plastic containers for food

Spare Parts (priority often depends upon how remote the project location is):
Tune-up replacement parts for all motors
Extra water pump seals and bearings
Extra compressor & alternator belts
Rebuild kit for air compressor
Extra air compressor?
Rebuild kits for dive regulators
Extra dive regulators?
Repair kits for diver air lines
Extra diver air lines?
Extra air fittings
Extra water pressure and intake hoses
Extra water hose fittings
Extra rubber hose seals (each size)
Extra foot valve(intake for water pumps)
Extra suction hose?
Extra face mask(s)
Extra starter & alternator & fuel pump for dredge motor?
Spare tire (if dredge has removable wheels)

 

 
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This story first appeared in Gold & Treasure Hunter Magazine Nov/Dec, 1989 on Page 20.
This issue is still available! Click here.

By Dave McCracken

The efficiency with which the over-sized material is moved out of the way has a direct impact upon how much gravel and gold will be directed up the suction nozzle!

Dave Mack

 

 

Dredging technique in gold-bearing streambeds mainly is focused upon removing the over-sized rocks (any rock which is too large to be sucked up the suction nozzle) from the work area of the dredge-hole. In most hard-packed streambeds, this removal of the over-sized material is the bulk of the dredger’s work. From a production stand­point, a large portion of this work has to do with freeing and removing the over-sized rocks from the stream­bed in an orderly fashion.

Hard-packed streambeds are laid down in horizontal layers during major flood storms. Generally, the streambed is put together like a puzzle, with different rocks locking other rocks into place. Usually, because of gravity, rocks higher up in the streambed (laid down later) are locking lower rocks (laid down earlier) into their position within the streambed.


Because of this, we have found the best means of production is to dredge the hole down a layer at a time. We call this a “top cut.” If you take down a broad horizontal area of the streambed all at once, you uncover a whole strata of rocks which are interconnected like a puzzle. Then, you can see which rocks must be removed first so that you can free the others more easily. This really is the key to production dredging!

Generally, there are two things that drastically slow down the production of less-experienced gold dredgers: (1) plug-ups and (2) “nitpicking.”

The time and energy spent freeing plug-ups from the hose and power-jet cuts directly into how much progress will be made in the dredge-hole.

Plug-ups are caused by rocks jamming in the dredge’s suction hose or power-jet. Everyone gets a few of these. Inexperienced dredgers get many! This comes from not understanding which types of rocks, or combination of rocks, to avoid sucking up the nozzle. Basically, this knowledge comes from hard-won experience in knocking out hundreds or thousands of plug-ups until you reach the point where you become more careful about what goes into the nozzle. I have covered this area quite thoroughly in my “Gold Dredger’s Handbook”

During the past several years, some dredge manufacturers have started building dredges using over-sized power-jets. This means that the inside-diameter of the jet-tube is not reduced in size from the inside diameter of the suction hose, helping to greatly reduce the number of plug-ups a dredger will get while in production. Because of this, an oversized jet would be high on my personal priority list if I were in the market for a dredge!

So, the combination of some practice in learning which types of rocks to avoid sucking up the nozzle, and the over-sized power-jet on modern dredges, will eliminate most of the plug-ups that would otherwise hinder production.

The other main loss of production, which we are all guilty of to some extent, comes from a poor production technique which we call “nitpicking”. Nitpicking is when you are trying to free rocks from the streambed which are not yet ready to come out. Nitpicking is dredging around and around rocks which are locked in place by other rocks that need to be freed-up first. Nitpicking is when you are doing things out of the proper order!

When you find yourself making little progress, the key is almost always to widen your dredge-hole.

Production dredging means moving gravel through the nozzle at optimum speed. This is accomplished by making your hole wide enough to allow the over-sized rocks to be easily removed. As soon as you find the rocks are too tight to come apart easily, it is usually time to widen the hole again or take the next top cut. “Top cut” is the term we use to describe when we take a bite off the top-front section of a dredge hole to move the working face forward. “Working face” is the portion of the excavation that we are mining.

An underwater dredging helper can be a big help to remove over-sized material from the dredge-hole. Basically, there are two completely different jobs in an underwater mining operation: (1) nozzle operator (N/O) and (2) rock person (R/P). The nozzle operator is responsible for getting as much material up the nozzle as possible during the production day. Therefore, it is his or her responsibility to direct how the dredge-hole is being taken apart. The rock person has the responsibility to help the nozzle operator by removing those rocks that are immediately in the way of production.

Since there are plenty of over­sized rocks that can be removed from a production dredging operation’s work area, it is important that the R/P have some judgment as to which rocks ought to be moved first. Ideally, he will pay attention to what the N/O is doing, and focus his or her efforts primarily on those rocks which are immediately in the nozzle’s way.

The rock person should be moving the very next rock that is in the nozzle’s way.

Silt is usually released when a rock is moved out of the streambed. So an R/P must be careful to not “cloud-out” the hole (loss of visibility). This can be avoided by concentrating on (a) moving those rocks that are near to where the N/O is working (this is the first priority), or (b) moving those rocks that have already been freed from the streambed, but not yet removed from the hole.

On occasion, an R/P unwittingly takes over the production operation by randomly moving whatever rocks he or she happens to see. This then causes the N/O to have to follow the R/P around, sucking up the silt which would otherwise cloud-out the dredge hole. This generally results in slowing down production. We have found that it is much better if the R/P accepts the position of being the N/O’s assistant, which allows the latter to direct the progress of the dredge-hole.

The nozzle-operator should communicate with his helpers where he wants to take a cut off the front of the hole.

Since production is controlled by how efficiently rocks can be removed from the dredge-hole, it is important to understand that they must also be strategically discarded in a manner which, if possible, will not require them to be moved a second or third time. Generally, this means getting each rock well out of the hole–as far back as necessary. Good judgment is important on this point. You only have so much time and energy available. How far that over-sized rocks will need to be removed from the hole is somewhat dependent upon how deep the excavation is going to go. Early on, we often must guess about this. Sometimes, the streambed turns out to be deeper than we thought it would be. Then, we find ourselves turning around and throwing all the cobbles further back away from the hole. This is not unusual.

We also must use our best judgment to not waste our limited time and energy resources. We really do not want to move all those tons and tons of rocks any further than necessary to allow a safe, orderly progression in the dredge-hole.

As we move our hole forward, and as we dredge layers (“top cuts”) off the front of the hole, we try to leave a taper to prevent rocks from rolling in on top of us. This is an important safety factor. Also, since the N/O’s attention is generally focused on looking for gold, the R/P should be extra vigilant in watching out for safety concerns. Any rocks or boulders that potentially could roll in and injure a team-mate should be removed long before they have a chance to do so.

The rock-person’s attention should always be on safety. If there is danger, he or she should point it out immediately to the Nozzle-operator.

Some rocks will be too large and heavy to throw out of the hole. Therefore, it is good technique to leave a tapered path to the rear of your hole so that boulders can be rolled up and out. If you cannot remove boulders from your hole, the hole may become “bound-up” with over-sized material. This can create a nitpicking situation. It is important to plan your excavation to allow you a certain amount of (safe) working area along the bottom of your dredge hole so you can stay in balance while working.

If you see boulders being uncovered which are too large to roll out of the hole, you should immediately start making room for them on the bedrock at the back of your hole. You normally accomplish this by throwing or rolling other rocks further behind. This takes planning in advance.

Winch Operator Watching Closely For Diver Signals

Boulder In Sling

Sometimes winching is necessary to remove large boulders or an abundance of large rocks from a dredge-hole. However, because winching takes additional time, the pay-streak usually must contain more gold to justify the time and effort that is required.

The amount of streambed material that you are able to process through a gold dredge will determine the volume of gold that you will recover. Actually, this volume-to-recovery ratio is true of any type of mining operation, whether it is a large-scale lode mine, a small-scale miner using a gold pan, or anything in-between.

The smaller the amount of material that a dredging program has the capacity to process, the richer the pay-dirt must be to recover the same amount of gold. Consequently, a smaller-volume operation often needs to invest more time and energy into sampling to find the more-scarce, higher-grade pay-streaks. For this reason, smaller-volume operations generally spend more time sampling, less time in production; and, therefore, usually recover less gold. But not always!

Having said that, I should also say that successful gold recovery depends upon more than the size of the dredge. A lot has to do with the skill of the operator(s).

As a general rule, gold mining on any scale is volume-sensitive. If you can dredge twice the volume of streambed material, not only can you recover twice the amount of gold, but you may find (many) more lower-grade gold deposits which can be productive when developed. You can also dredge deeper sample holes. This allows you to reach deeper pay-streaks. This is why we always advise beginning gold dredgers to go out and find an easy location where they can practice their basic gold dredge production techniques to improve their speed before they begin a serious sampling program.

It is a good idea to practice your dredging skills, so that you can operate the nozzle efficiently while moving your own oversize material out of the way.

An inexperienced dredge-miner will sometimes be so slow in volume-production, that he or she may miss valuable pay-streaks simply for lack of being able to process enough gravel, or lack of ability to dredge his or her sample holes large or deep enough during sampling. An inexperienced dredge operator also may not even be aware this is the problem.

When you dredge a sample hole, you must evaluate how much gold you recover against the amount of time and work it took to complete the test hole. If you are only moving at 20% of your potential production speed, you easily can make the mistake of walking away from excellent pay-streaks just because you will believe they are not paying well enough.

When we run larger-sized (8-inch or larger) gold dredges, we almost always have at least two divers working together underwater. The reason for this is because running an eight or ten-inch dredge in six feet or more of streambed material requires that an overwhelming number of over-sized rocks must be moved all the way out of the dredge-hole by hand. This varies from one location to the next. But generally, in hard-packed, natural stream-beds, somewhere between 60 and 75 percent of the material is too large to process through an eight-inch dredge. This is where second and third persons become a big help. A sole-operator in this type of material, when it is deeper than five or six feet, is going to spend a great deal of time throwing rocks out of the hole, rather than operating the suction nozzle.

The smaller the dredge, the shallower the material that a single operator will be able to manage efficiently. Also, some hard-packed streambeds require that most of the over-sized rocks be broken free with the use of a pry bar. This further decreases the amount of nozzle-time on a single-person dredging operation.

In the final analysis, it is the volume of material that is sucked up the nozzle (in any given location) that determines gold production. However, the efficiency with which the over-sized material is moved out of the way has a direct impact upon how much gravel and gold will be directed up the suction nozzle. So, gold production ultimately is controlled by how well the over-sized material (rocks too large to pass into the suction nozzle) is managed. The nozzle-operator’s focus, therefore, should be on directing the nozzle to suck up the gravel that will make it easier to free more over-sized rocks, rather than indiscriminately sucking up any gravel in the hole. In other words, the Nozzle operator should be actively pursuing a plan that keeps the Rock person busy right there where the action is happening!

If a rock person(s) is added to the operation, he or she must increase the program’s efficiency by at least as much as the percentage of gold which he/they is going to receive. This is not difficult to accomplish if conditions are right and the dredging team is organized.

On the other hand, if you are operating a dredge in two or three feet of hard-packed streambed, adding a second person may not increase your production speed enough to make it worthwhile to pay him for his time. This is because the material is shallow, and you may not have to toss the over-sized rocks very far behind in the dredge hole (less effort required to make progress).

When I am operating a production dredge in five or six feet (or more) of streambed material, I can literally bury a rock person with over-sized rocks, and make my helper work like an animal all day long. I also have to work like an animal to accomplish this. The result is a good-paying job for my helper and a substantial increase in my own gold recovery.

When I find myself working in eight or ten feet (or more) of material, I must have at least one or two (or more) rock person(s) to help me. Otherwise, I will be completely buried with cobbles and over-sized rocks all day long and will get in very little nozzle-time.

All of this also applies to smaller-dredge operations. Your ultimate success will be directly proportional to how much material you can get up the nozzle of your dredge in the right locations. The more efficiently you can make that happen, the quicker you will get your nozzle into pay-dirt.

Large-rock management is important! Since most of the material in a natural, hard-packed streambed will be too large to go through the suction nozzle, the progress and speed of your operation will directly depend upon how quickly and efficiently the oversize (cobbles and boulders) materials are moved out of the N/O’s way. Dredging is not just a matter of sucking up some gravel; at least not in the places where most pay-streaks are found.

As shown in the following important video segment, in most pay-streaks, the only gravel that gets sucked up is that which is found between the over-sized rocks. So the key to continued progress depends upon management of over-sized material:

A cutter-head consists of a rotating series of hardened-steel blades that are designed to cut into sand, clay or classified gravel. It does not have the capability to cut through hard-packed streambeds that are made up of over-sized rocks and boulders.This is the reason that cutter-head dredges do not work well in hard-packed streambeds; because they are continuously up against rocks that must be moved out of the way by divers. But it is too dangerous to put divers in a dredge excavation where a cutter-head is operating.

So, there is a lot of good to be said about organizing a system to get the rocks moved out of your way as quickly and efficiently as possible. This is true in dredging on any scale and regardless of whether you are working alone or with a team.

The reason why larger dredges can get more accomplished in gold-bearing streambeds is usually not because they will suck up more gravel. It is because a larger hose and nozzle will suck up a bigger rock. Every rock that can go up the nozzle is a rock that does not need to be packed out of the dredge-hole by hand. This is the primary factor that speeds things up with a larger dredge.

Another major advantage of a two-person team is the substantial amount of emotional support which a second person can add to the operation—especially when you are dredging in deep material, or when you are sampling around for deposits and have not found any in awhile.

On the other hand, the wrong person can inhibit the operation, either physically or emotionally. So, you must be especially careful to select teammates who have work ethics, moral standards and emotional endurances that are similar to your own.

In my own operations, we have found that the key to good teamwork is in establishing standard operating procedures for nearly everything we do. We also work out standard underwater signals. This takes quite a bit of planning and communication in advance, and it is an ever-continuing process. We have standard procedures for removing plug-ups from the hose and jet. We have standard procedures for moving the dredges forward and backward during operation. And, we have standard procedures for every facet of the underwater work — from moving the raw material that is in front of us, to the placement of tailings and cobbles behind our dredge-hole.

As noted above, volume is the key to success—at least to the degree of success. We take this aspect of the work quite seriously in my own operations — to the point where every single moment and every single physical effort is regarded as important to the operational-moment while we are dredging. You will never find the members of my team socializing or goofing-off during the underwater production hours. We allow ourselves to relax during the off-work hours and lunch break. But during production-time, we are entirely focused on the needs of the operation. We treat the dredging-portion of the operation like a competitive team athletic sport. We are not competing against each other. In a team effort, we compete against the barriers that Mother Nature has constructed for us to overcome so that we can recover volume-amounts of gold. To us, our teamwork is kind of like running a relay race. It is rewarding this way when we really synchronize our efforts.

We try to spend a minimum of six hours doing production-dredging or sampling each day. In our operation, this is normally done in two three-hour dives. Other commercial operators prefer three or four shorter dives. I know one commercial dredger in New Zealand who prefers a straight six, seven or eight- hour dive. What an animal!

I like lunch. But, I also agree with the concept of long dives; the reason being that it takes a while to get a good momentum going underwater. Every time you take a break, you need to get that momentum going all over again. What do I mean by “momentum?” Momentum in dredging is very similar to the beat of the drum in driving music. It is the continuous flow of gravel up the nozzle, with the over-sized rocks being moved out of the way in their proper order at just the right moment so that the flow of material into the nozzle is never slowed down. It is everyone doing whatever is necessary to keep that flow happening. It is about synchronizing the right rhythm at optimum speed, and keeping the beat going!

In fact, team-dredging can be kind of like an art form. It is similar to playing music. Only, instead of notes being played on several instruments to form a harmonious melody, the team produces a stream of coordinated effort, using their bodies to move the suction nozzle and the over-sized rocks, in concert, so that all of the effort works together to achieve optimum momentum and harmony.

In his or her initial enthusiasm, an inexperienced R/P may, rather than move the next rock in the path of the N/O, instead, move the wrong rock and cloud-out the dredge-hole with silt. This causes the N/O to be slowed down (1) because of the decreased visibility, and (2) because he or she must now take the time to move the proper rock out of his own way. This is the equivalent of “playing off key,” or playing the wrong musical selection. Everybody else is playing one song, while the new guy is doing something entirely different. The bottom-line for your dredging operation: less volume through the suction nozzle, and less gold at the end of the day.

On the other hand, there is enormous personal and team-satisfaction to operating within a well-structured team-dredging system. Such a system functions best when the N/O is the conductor, and the R/P plays a supporting role, anticipating in advance and taking every possible action to contribute to the N/O’s momentum.

Four-man team on Author’s commercial operation. Notice how everyone is involved up where the action is happening at the suction nozzles.

This is not just about the next rock which is in the way of the nozzle. It is also about moving the dredge forward a bit as necessary to give the N/O a little more suction hose when it is needed. It is also about the dozen or so other things that are necessary to keep the flow going without a lag.

Volume-momentum is lost every time the N/O has to put the nozzle down to take care of something. That will impact directly upon the success of the operation. Every effort should be made to keep this “down time” to a minimum.

Since volume is really the key, in my own operations, we try to treat dredging pretty-much like a team sport – competitive and physical! When I give my R/P the plug-up signal, he races to the surface to quickly clear the obstruction. He doesn’t just mosey on up there. He moves up there, like running for a touchdown or rounding the bases for the winning home run. This is also the sense of urgency with which he returns to the hole as soon as the plug-up is free. When he sees that rocks are stacking up in the hole, he doubles his pace to catch up. When caught up, he looks around to see where other cobbles might be moved out of the way, without clouding the hole. Or, he might grab the pry bar and start breaking rocks free for the nozzle operator. At the same time, when I am operating the nozzle, I am doing my own job—getting as much material through the nozzle as humanly possible while uncovering new rocks to be moved by the R/P, with the minimum number of plug-ups. And, I do not stop for anything if I can help it. If something else needs to be done, I delegate it to my R/P or other helpers so that I can keep pumping gravel up the nozzle. That’s my job! Everyone’s gold-income depends directly upon how much material is sucked up.

While this statement is also true when you work alone, every effort counts for something in production team dredging. Therefore, everyone needs to pay attention to what is going on in the dredge-hole. R/P’s particularly have to be able to switch gears quickly. At one point, there may be a pile of rocks which needs to be thrown out of the way. The next moment, even before the R/P has moved many of those rocks, he or she may notice something else that is directly impeding the N/O’s progress—like a boulder that needs to be rolled out of the way, or a particularly-difficult cobble which needs to be broken free with the pry bar. The main objective in everyone’s mind should be to support the N/O’s progress. Whatever impedes his progress should be the priority and get immediate attention.
The key to a productive underwater support person is having him or her work to help keeping gravel flowing into the suction nozzle.

The only time I intentionally slow things down is when I am uncovering the gold. I have to keep an eye on that to follow the pay-streak. However, as explained in the following important two video segments, you can also slow down too much by looking. You have to find the proper balance between looking and getting volume up your nozzle:

If the pay-streak is good, I also point out the gold to my helpers as I uncover it. There is emotional gain from this. Everyone deserves the boost. The gold eventually gets spent or hidden away. The memories last your entire lifetime! As demonstrated in the following video sequence, there are few things in life that will give you a bigger emotional boost than finding one of Mother Nature’s rich golden treasures:

As the following video segment demonstrates, once you locate a high-grade pay-streak, it is also very important to invest enough time to locate the downstream and left and right outside boundaries of the deposit. This is to make sure that you are able to develop the whole deposit without burying part of it under tailings or cobbles:

When things get too confused inside the dredge-hole, sometimes the N/O must put down the nozzle and help organize in the hole (move cobbles and boulders out of the hole). But, everyone should be keenly aware of the operational situation that actual production momentum (gravel up the nozzle) has stopped and that it needs to get underway again just as soon as possible.

As noted earlier, and demonstrated in the following video sequence, we take top-cuts off the front of the dredge-hole in production dredging, and we take the material down to the bedrock in layers. We do this because it is the fastest, safest, and most organized method of production dredging:

Sometimes, when conditions are right for it, an R/P may be working right next to the nozzle, breaking the next rock free and quickly throwing it behind in the hole. However, on every top-cut, there comes a time when the N/O decides to drop back and begin a new cut to take off the next layer. The R/P has to pay close attention to this and follow the N/O’s lead. Otherwise, he or she might finish breaking free a rock up in the front of the hole when there is no-longer a nozzle there to suck up the silt. That would be an error.

In other words, the R/P has to keep one eye on what the N/O is doing all the time. Because, if the N/O is a dynamic and energetic person, he or she certainly will not be following the R/P around the dredge-hole. The N/O has to orchestrate the effort. So all of the support-players should be paying close attention and assisting in the N/O’s next move. A good nozzle operator takes apart the hole with an organized method that is easy to follow by the others.

Teamwork also extends up to the dredge-tender on the surface, if you have one. The dredge-tender should continuously monitor the water-volume flowing through the sluice box. If it visibly slows down, he should suspect a plug-up and take steps to locate and clear it. Sometimes, the water-volume has been reduced simply because the N/O has temporarily set the nozzle down over a large rock in the hole. But, on the occasions when there is a plug-up, it is a mark of great teamwork to have a tender handling the problem immediately without having to be told. Volume through the sluice box should also be continuously on the tender’s mind. When gravel stops flowing, he or she should be thinking that something might be wrong.


When the flow slows down through the recovery system, the tender should just assume there is a plug-up that needs to be freed up from the surface.

That same level of anticipation and teamwork should also apply in other areas, as well. When the tender sees that the dredgers are moving forward in the hole, he should ensure that the dredge is being moved forward accordingly. This is so the N/O will always have a comfortable amount of suction hose to work with. As demonstrated in the following video sequence, different-sized dredges require different lengths of suction hose to allow the nozzle operator a comfortable amount of movement and flexibility:

Good teamwork involves a lot of close observation and timely anticipation to minimize the number of actual orders that need to be given and the consequent amount of down-time. Most of the activity is handled by standard operating procedures which require some planning and communication in advance.

As you might imagine, there are some different opinions about all of this. Some people are simply not running any races. This is fine; but they must understand that they do not have the same gold-recovery potential as others who are working at a faster pace—or, with a more organized system.

Generally, you will not hear anyone on my team complaining—especially when it is time to split-up the gold that we have recovered.

There is not anything difficult to understand about successful gold dredging techniques. The process is quite simple. Serious dredging on any scale is a lot of hard work. Volume is the game! The faster, deeper and more efficiently you can dredge the sample holes, the faster you will find the pay-streaks—and, the better you will make them pay. Even with smaller dredges.

At the times when you are not finding commercial amounts of gold, there is at least the satisfaction of knowing that you are accomplishing optimum performance. And, when you do locate the deposits, the sky is the limit!

 

 

By David R. Toussaint

Professional Gold Hunter’s Strategy Leads to Pockets of Gold

 

PrestonPreston poses with his collection which came from a pocket in northern Nevada.

A professional electronic gold prospector in Arizona has developed a gold-hunting strategy that has led to the discovery of more than 100 ounces of gold during the past few years. Preston Vickery, 42, of Kirkland, Arizona has used his gold-hunting strategy, which he calls “pocket hunting,” to find in-place gold in hard-hunted areas that have only frustrated other electronic prospectors. Now he’s ready to share his strategy with the world:

“Most others are stuck in the (placer) nugget mode,” says Vickery about other electronic prospectors. “They should be doing the whole area when they hunt for gold. You do placer and you do hardrock hunting.” Vickery has the right credentials to create his own method of gold hunting. While not a graduate of any mining school, Vickery got his education in prospecting from real-life experience and a family tradition. He’s been a professional gold prospector since his early-20’s and has also worked every facet of mining. “I’ve made a living,” Vickery says modestly. “I haven’t gotten rich, and I haven’t been on welfare.”

You might say prospecting is in the Vickery blood. Preston’s father was also a professional gold prospector and miner. The elder Vickery taught his son all he could about prospecting, including the geological indicators associated with gold formations. Now in his 90’s, Preston’s father is too old to get out much, but he still has a few things to teach his son about gold prospecting. Tracing the Vickery bloodline back even further, Preston’s grandfather was also a professional miner and prospector. Grandpa-Vickery spent much of his life working in lead and gold mines, and he wasn’t shy about passing on his knowledge to his son. Thus, Preston’s grandfather started a family tradition that has created three generations of prospectors and miners.

Now, when Preston goes prospecting, he uses the accumulated gold-hunting wisdom of three generations. Preston has been fairly successful over the years, but his gold-finds began to dwindle during the mid-1980’s. Most of the good nugget-hunting areas were being hunted-out, and it became harder and harder to make a living as a prospector.

It was about that time that Vickery bought a Fisher Gold Bug metal detector. “Once I saw what a Gold Bug could do, it wasn’t long before I bought one,” he remembers. One time out on the Arizona desert, Vickery watched a famous nugget shooter amaze a group of electronic prospectors. This top-notch nugget shooter waited until the other prospectors in the group were satisfied that a nugget patch they were hunting was thoroughly cleaned out. After asking permission, he swept the patch one more time with his Fisher Gold Bug, finding another two or three small nuggets. “He was the best I’ve ever seen,” says Vickery.”He worked quickly but thoroughly. He taught me how to clean out a nugget patch.”

Even though Vickery learned how to clean out a patch in the late ’80’s, fewer and fewer nugget patches needed cleaning out. It seemed like every place the old-timers found gold had already been hunted to death. Vickery could spend all day hunting and only find one or two nuggets. These finds might excite a weekend prospector, but they were not enough for someone whose livelihood depends upon finding nuggets. There had to be a better way. Contemplating his predicament, Vickery began to piece together things his father had taught him and things he had learned himself. The result was a new approach to gold hunting that he calls “pocket hunting.”

Using this new method, Vickery’s luck began to change; and he soon found three nice pockets of gold. What is a “pocket” of gold? “To understand this, you must first understand how gold ‘makes,’” says Vickery. The story begins thousands, maybe millions, of years ago. First, the earth splits, forming cracks and fissures. These fissures form an intricate structure of veins that sometimes reach a hundred miles across the earth’s surface. A second movement of the earth, such as an earthquake, is required to create the right conditions for gold to form within this system of cracks. If this second movement occurs, an “intrusive” can be formed, allowing chemicals and minerals to enter the crack. Gold forms if the right chemicals and minerals are present in the right concentrations. “Gold is just a quirk in the way nature works,” says Vickery. “All it is, is a big break in the earth’s surface. These cavities are usually cracks that develop into veins. Small veins sometimes pocket-out into kidneys. These fill up with solutions and sometimes gold is formed.”

These “kidneys” or “pockets” along the cracks in the earth are what Vickery looks for when he hunts for gold. He says that it is possible to predict the location of these pockets by visualizing the structure of cracks in which gold has a chance to form, or “make,” as Vickery says. These pockets of hardrock gold do not usually contain as much gold as the main vein that the old-timers mined, but 30 or so ounces of gold is nothing to sneeze at.

These cracks in the earth’s surface, which develop into veins, usually form along parallel lines, all traveling in roughly the same direction. To find the pockets of gold, Vickery extends the boundaries of his search area away from the historical diggings. He tries to visualize the system of cracks that gave the gold places to “make.” Many small pockets of gold could have formed along this system of cracks, sometimes up to 500 or more feet away from the original outcropping. “You go in the area where gold has already been found. Then you look for the way the structure (of veins) is running,” Vickery says. “You just try to put yourself in the area where gold has a chance to’ make.’”

“Smaller veins that formed parallel to the main vein were difficult for earlier generations of miners to find, especially without metal detectors,” Vickery says. The old-timers followed a vein by digging. If they did not see any more gold in their pan, they gave up and stopped digging the vein. If the vein picked up again farther on, or if a splinter vein made a small pocket of gold away from the main vein, the old-timers had no way to find it. “The old-timers would have dug along the vein for some distance to see if it would ‘make’ again,” Vickery explains. “The old-timers couldn’t get all the tiny splinter veins. Sometimes they were too far away. They didn’t have the technology to find them like we have today.”

Using his metal detector, Vickery found a nice pocket of hardrock gold on a prospecting trip to northern Nevada. But the trip did not start out on a happy note. Two days of hunting a well-known area near some historical diggings had produced only a few small nuggets. Putting his pocket-hunting strategy into service, Vickery found a 30-ounce pocket of in-place gold just a couple-hundred feet away from the hard-hunted old-time diggings. About four feet deep, the pocket had formed along a smaller vein that ran parallel to the primary vein which the old-timers had mined. Hidden four feet below the surface, the pocket gave off a strong signal when he passed his detector coil over it.

So what is the first step when pocket hunting for gold? The first thing Vickery does when he starts hunting an area is to climb a hill. Using binoculars, he studies the entire area and draws a map with reference points to provide bearings while he hunts. Next, he looks for gold indicators, cubes or clods of iron oxidation that form an “oxide zone” around the historical diggings. Patterns in the oxide-zone, like strings of red earth, that suggest a crack in the earth where iron formed, can also indicate a vein. Often times, if iron formed in a crack, gold also could have formed in another nearby spot along the same crack.

In particular, Vickery looks for any place that the red oxide lines shifted, forming a broken line. This shift could have created an intrusion that allowed gold to form a pocket within the crack. Visualizing the system of veins in the earth, he starts hunting, by searching right on top of the main vein, tracing about 400-to-500 feet to see if it picks up again in a spot unknown to the old-timers. If it doesn’t, he then drops downhill about 20 feet from the main vein and begins hunting in a line parallel to the main vein, now attempting to discover any pockets in splinter veins. Again, he hunts to a distance about 400-500 feet away from the original diggings. If his detector remains silent, he drops down another 20 feet and repeats the process.

If he finds any gold nuggets while searching, Vickery marks the spot and searches uphill to find the in-place pocket where the nuggets originated. If he finds a concentration of gold nuggets, he carefully works out where the concentration begins, where it occurs in the highest concentration and where it thins out. Then, using the edges of the concentration as two points of a triangle, he knows the third point of the triangle will be somewhere directly uphill where the nuggets originated. So he begins searching directly uphill from the highest concentration of nuggets. Vickery says he picked-up this method of triangulation in “Gold Canyon,” a novel by Jack London.

Pocket hunting for gold takes considerable concentration; it isn’t as easy as simply locating an old-time mining operation and swinging your metal detector around. You have to keep your hopes up, and not let yourself become discouraged. Pocket hunting provides the electronic prospector with a strategy for gold hunting that can result in more than an occasional placer nugget.

 

By Dave McCracken

You have a substantial prospecting-advantage with a modern gold detector!

Dave McCracken

 

 

woman with a gold nuggetI highly recommend The Fundamentals of Electronic Prospecting be read before reading this article.

All the rules of placer and desert geology apply to gold nugget hunting, and this knowledge should be utilized to establish where gold deposits and nuggets are most likely to be found.

Particular attention should be paid to locations which have little or no streambed or other material present, so the detector’s coil can search as closely as possible to bedrock or false bedrock layers. Also, exposed tree roots along the edges of the present streams, rivers and dry-washes have been proving successful, especially along the smaller tributaries in the higher elevations of known gold country.

Some of the most productive areas for electronic prospecting in the dry regions are in the near vicinity of old dry-washing operations. The old-timers were only able to make dry-washing work in very high-grade areas. They seldom recovered all the high-grade gold out of an area, because they did not have the means or equipment to prospect extensive areas. You have a substantial prospecting-advantage with a modern gold detector. Natural erosion over the years has likely uncovered more high-grade in the immediate area, or concentrated other spots into new high-grade gold deposits.

When prospecting old dry-wash workings, it is always worth a little time to rake back some of the old tailings piles and scan them with your detector. Dry-washers, today and during the past, almost always used a classification screen over the feed area. The screen was commonly around half-inch mesh. An operation shoveling onto the screen at production speed in dry high-grade gravel might have missed larger nuggets as they rolled off the top of the screen. Sometimes, when working a layer of caliche, if the material was not broken-up well enough, it would roll off the screen with nuggets still attached. A metal detector reads out strongly on these kinds of targets. Make sure to ground-balance to the tailing pile. One nice thing about prospecting in these tailing piles is that they usually are not filled with iron trash targets.

When dealing with natural streambeds above the water, you generally do not find too many other reading metallic objects besides gold, unless the spot which you are scanning is near an inhabited location, like a park or an old dump. So it is reasonably safe to dig any target that gives off a metallic reading in a streambed.

However, some locations have lots of trash and small iron targets. Sometimes, iron targets seem to accumulate heavily in the same areas as gold. This presents a big challenge! Once you have been scanning a particular area for a while, you will gain an understanding of how much “trash” (metallic objects of no value) exists within the vicinity. With some experience on gold objects, you will learn to distinguish the different tone changes between most gold objects and most trash targets. Pay particular attention to the very faint readings, as is often the case with natural gold targets.

One of the main keys to successful electronic prospecting is to slow down your sweeping action. You cannot do it fast like when hunting for coins. You almost have to crawl across the ground. Remember, you are listening for even the faintest whisper of a sudden increased threshold hum. A gold target may sound like a coin—only a quieter signal.

Different types of detectors have special non-motion or pinpointing settings which allow the coil to be moved very slowly and still pick up targets. This means you are able to slow down your sweep to almost a standstill and still hear a target as the coil moves over it. On the other hand, these settings may be too sensitive to use for nugget hunting on some detectors, depending upon field conditions and how fast you are sweeping. When in doubt, experiment while using a test-nugget on or in the ground you are searching.

Another important point is to overlap your coil sweeps. The area covered by the search-field under your coil is similar to a triangle. Directly underneath the coil, the search area is about the same size as the diameter of your coil. The search area becomes narrower as it penetrates the ground further away from the coil.

However, the size of this triangular search-field is not constant underneath the coil. It changes as mineralized conditions change in the ground below your search coil. If you do not overlap your search strokes, you can leave as much as 50 percent or more of the area below the search coil behind, without being adequately searched.

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You have to use your own judgment about how to discriminate between which targets to dig, and which to leave behind. This comes with practice and experience. Discrimination of any kind, whether by electronic circuitry or the audio sounds given off by the target, has limited accuracy. The depth of a target and the degree of ground-mineralization in that particular location can confuse any discriminator. In some places, you will want to dig every target. In other places, where there is lots of trash, you may find it more productive to discriminate your targets by sound and/or in combination with electronic discrimination features on your detector. In this case, you have to balance the need to leave some small pieces of gold behind, with not wanting to dig a bucket full of trash and valueless iron targets; and therefore, less gold.

When in doubt, dig! Or at least toss your sample nugget down and get a comparative reading.

With lots of practice in the field, you will eventually reach the point where your metal detector is like an extension of your arm—like an extension of your perception and knowingness. You will gain the ability to look down into the ground and have a pretty good idea of what is there.

Big nuggets are generally not too difficult to find. In most areas, however, there are hoards of smaller gold targets in ratio to each large nugget found. Small pieces of gold are your bread and butter! Most gold is small gold, but it has to be large enough to be worth your while. Some of the modern gold detectors will pick up pieces of gold so small that you could be finding them all day long; and at the end of the day, not have accumulated very much gold by weight. In this case, you may want to move to a different area.

Just like in other forms of gold mining, electronic prospectors have to set standards for themselves. Someone pursuing the activity to make money will be motivated to recover volume-amounts (by weight) of gold. Another person pursuing electronic prospecting as a part time activity may receive his or her best thrills by recovering the smallest-sized targets.

One interesting development in the electronic prospecting field, which I have not seen happen in other gold mining activities, is the tremendous emotional success gained from finding extraordinarily-small pieces of gold. Normally, in gold prospecting, we get excited to find a big nugget or a rich deposit. These are easy to locate when scanned over by a metal detector. The big challenge with a metal detector is in locating the smaller pieces. Experienced prospectors know that if they are finding the small pieces, they will easily-find the big pieces.

When scanning, keep your coil as close to the ground as possible. It takes a coordinated arm and wrist-action to keep the bottom of the coil parallel and close to the ground throughout the full sweeping action. Allowing the coil to move one or two inches away from the ground during the outside of a sweeping motion will also reduce depth-penetration by one or two inches. This will certainly result in lost gold targets. You have to practice keeping the coil close to the ground. Shorter sweeps is usually the answer.

Sometimes it helps to kick rocks out of the way, or use a garden rake to remove multiple smaller obstructions before you search an area. This allows you to keep the coil close to the ground with minimum obstructions.

During your prospecting activities, it is possible that you may find occasional targets which could potentially be classified as artifacts. The Archaeological Resources Protection Act defines just about anything you might find as a “protected” artifact. There are criminal penalties for disturbing or removing artifacts. What constitutes a protected artifact is primarily up to the judgment of local bureaucrats. Searching for natural gold targets is legal. Messing around with old junk and trash may be illegal. Sometimes, it is better to just leave old items where they lie. You will have to decide.

The main suggestion I commonly give to beginners about electronic prospecting is to not give up. With practice and by working in the right area, you will surely find some gold!

PINPOINTING

When you do have a reading target, its exact position in the ground should be pinpointed. This can be done by noting when the detector sounds out while scanning over the target in fore and aft and left to right motions. A steel or iron object can be often be distinguished by noting the size and shape of the object during the pinpointing process. Sometimes trash objects are large and/or lengthy in size.

Sometimes a stronger-reading target will seem to cover a larger area than it actually does. If you are having trouble getting an exact location, continue to lift the search coil higher off the ground while scanning with an even back and forth motion. As the coil is raised higher, the signal will become fainter; but the position of the metal object will sound-out at the very center of the search coil.

PINPOINTING WITH THE GOLD PAN IN WET AREAS

Once you have pinpointed the exact position of a target in an area near water, one way of recovering the object is to carefully dig up that portion of ground, using a shovel or digging tool, and place the material in your gold pan. Here is where a large plastic gold pan comes in real handy. Be careful not to cause any more disturbance or vibration of the streambed than is necessary while you are attempting to dig up a target. It is possible to miss the target on the first try and cause it to work further down into the streambed because of its greater weight in the wet environment. Sometimes you can lose the target, and not be able to locate it again with the detector.

Sometimes the ground is hard and needs to be broken up or scraped with a small pick. Keep in mind that a sharp blow from a pick can destroy a coin or disfigure a gold nugget, reducing its value. Digging and scraping is better than pounding, if possible. In hard ground, sometimes it is easier to loosen the material up and shuffle it into several small piles. These can then be flattened out and scanned to see which contains the target.

Once you have dug up that section of material where the target was reading, place it in your plastic gold pan and scan it with your detector. If the contents of the pan do not make your detector sound-out, scan the original target area over again. If you get a read in the original location, pour the contents of the pan neatly into a pile out of your way, pinpoint the target all over again, and make another try at getting the target into your gold pan. Continue this until you finally have the target sounding out in your pan. If you cannot see the target, and water is immediately available, pan-off the contents until the target is visible.

There is a good reason why you should not ever throw away any material from the target area until after you know for certain exactly what the reading target is. If you are looking for placer gold deposits and it happens that your detector is sounding out on a gold flake or nugget, the chances are pretty good of additional gold being present in paying quantities within the material which has been dug out of the hole, even if it does not sound-out on your detector. Remember, small particles of gold often do not make metal detectors sound-out. Therefore, the possibility exists that there could be hundreds of dollars worth of gold in a single shovelful of material not tightly-concentrated enough to cause your detector to sound-out. So wait until you have seen the reading target before you start throwing any material away.

If you dig for a target and then cannot get any further reads on the detector from either the pan or in the original target area, quickly pan-off the pan’s contents. There is always a possibility of a concentrated gold deposit which is no longer concentrated enough to read-out on your detector. In this case, you are most likely to have some of the gold deposit in your gold pan, which will quickly be discovered when you pan off the contents.

There is also another reason why you save the material from a hole until you have recovered your target. Because of the shape of a gold pan, and depending upon the size and shape of the coil you are using, if the gold target (especially a small target) ends up in the bottom of your pan, your coil may no-longer be able to scan close enough to the bottom of the pan to sound-off on the target. Because of this problem, gold pans have limited workability as a pinpointing tool in electronic prospecting. Sometimes, you can have better luck scanning the bottom-side of a gold pan.

DRY METHODS OF PINPOINTING

There are several popular methods of pinpointing reading targets in the dry regions where water is not available for panning. Some prospectors use a plastic cup. Material from the target area is scooped up and passed over the coil. If the contents of the cup do not sound-out on the detector, the target area is scanned again until the target is located. Take another scoop, pass it over the coil for a signal, and repeat until the target is in the cup. Then pour some of the contents into your hand. Pass the cup over the coil, then your hand, until you locate the target. Put the rest away in a neat pile, and repeat the process until you recover the object.

One important point to mention is that most search coils have equal sensitivity to targets both above and below the coil. In other words, during pinpointing, you can pass material over top of the coil and obtain the same results as if you turn the detector upside down and pass the material across the bottom of the coil.

Your handy magnet can be a big help when you are having difficulty finding a faintly reading target. Sometimes it is just a small piece of iron.

There is also the hand-to-hand method of pinpointing a target. You can reach down with your hand and grab a handful of dirt or material. Pass your hand over the coil to see if you are holding the target. Continue until you have the target in one hand. Then pass half the material in that hand to your other hand. Use the coil to find which hand has the reading target. Discard the material from the other hand and pass half the material from the reading hand to the second hand, again. Keep up the process until you only have a small amount of material in the reading hand. Carefully blow off the lighter material to locate the target.

Another procedure is to grab a handful and pass it over the coil as explained above. Once you have a reading handful, toss it in a pouch for later panning.

Some prospectors prefer to sprinkle a handful of reading material slowly on top of the detector’s coil. There are different ways to do this. One effective way, which requires some practice, is to sprinkle material over a slightly slanted coil while you vibrate it so that material slowly sweeps across and off. When the target drops onto the coil, the detector will sound-off with a distinctive bleep. Then, all you have to do is gently blow the dirt off the coil, or recover the target from the top of the pile where the material is landing. This method is nearly impossible in wet material.

One important thing about using your hands to pinpoint and recover gold targets, is that some of today’s most sensitive high frequency gold detectors react to the salt (mineral) content on or in your hand. When this occurs, your hand will give a reading when passed over the coil by itself, sometimes even a strong signal. This makes hand pinpointing methods more difficult. In this case, the plastic tray or cup works just fine, or the method of pouring material onto the coil.

If you find a gold target, be sure to scan the hole again. Sometimes it is worth doing a lot of digging and/or raking, with alternate scanning of the immediate area. Gold targets almost never travel alone! I have seen dozens of gold flakes and nuggets come from within a one-foot square area on bedrock. Many times!

HOT ROCKS

Sometimes you get soft or strong signals from your metal detector when the coil is passed over rocks which contain heavy mineralization. These rocks are called “hot rocks.” This needs to be clarified. It isn’t necessary for a rock to have an extraordinary amount of mineralization to sound-off as a hot rock. It just needs to have more than the average ground which your detector is ground-balanced to. The opposite of this is also true. A rock containing less mineralization than the average ground will change tone on a detector in the opposite way. These are called “cold rocks.” A hot rock from one location could be a cold rock in another location containing higher mineralization in the average ground.

Put another way, when your detector is properly ground-balanced to the average ground, it will sound-off on rocks containing condensed heavier mineralization. Often, the signals given off by these hot rocks can be mistaken for signals which might be given off by gold targets in the ground. Some locations have lots of hot rocks. Naturally, since gold travels with other heavy mineralization, you can expect to find hot rocks in the various gold fields.

Hot rocks come in all sorts of colors and sizes. A big hot rock, depending upon the degree of mineralization over the average ground, can sound very similar to a gold target. The same goes for small hot rocks.

Quite often, most of the hot rocks within a given area will be similar in nature, color and hardness, but not necessarily in size. After searching an area for a while, you will know what most of the hot rocks look like. This makes pinpointing targets a little easier, especially when dealing with small hot rocks. When receiving signals from rocks which are dissimilar to the average-looking hot rock of the area, check them out closely, especially when they have quartz. Some of these may not be hot rocks at all, but gold specimens.

If you are finding hot rocks on top of the ground, you will almost always find them buried, as well.

Metal targets gradually lose signal-strength in proportion to the increased distance from the coil. Hot rocks rapidly lose their signal-strength as they are scanned further from the coil. Also, a metal target tends to create a more specific, sharper signal as the coil is passed over. The signal given off by most hot rocks is not as sharp. It is more of a mushy sound which doesn’t have as clear a change in tone-intensity as the coil passes over the target.

When uncertain about a reading target, one way that some hot rocks can be identified is by passing the coil over the target from different directions. If the target only sounds out when being swept from one particular direction, then it is nearly certain that the target is not a gold nugget.

Sometimes, when lowering the sensitivity on your detector a few numbers, the signal given off by a nugget will continue, but weaker. A hot rock signal will quickly disappear by lowering the sensitivity. You can get a better idea how your detector is reacting to sensitivity changes by running it over your test-nugget.

Another test is to slowly raise the coil further away from the reading target as you are scanning. The signal of a metal object will become progressively fainter as the distance is increased. The signal given off by a hot rock will rapidly die away as just a little distance is put between the target and the coil. Most hot rocks in a given area will have a very similar sound, the intensity depending upon size and distance from the coil. Sometimes, you will find that a gold nugget gives off a much sharper signal. But not always. Much also depends upon the size of a gold target, its distance from the coil, and the amount of mineralization interference in the ground that is being scanned.

Each area is different. The hot rocks in some areas are reasonably easy to distinguish. In other areas, it is necessary to dig every signal.

Larger hot rocks are easier to detect. Many can simply be kicked out of the way. It is the smaller pebble-sized hot rocks which create faint signals. In some locations, these signals are so similar to the signals given off by gold nuggets that you have no other choice but to dig them up.

If lots of hot rocks are making it difficult for you in a particular area, you might try experimenting with smaller coils. Smaller coils are more sensitive to smaller pieces of gold. Therefore, the sharpness of the signal over gold targets is also intensified. This may give you the needed edge in distinguishing the slightly-different signals being given off by hot rocks in that area.

Some gold prospectors go so far as to ground-balance over top of a hot rock until it no longer gives off a signal. This will eliminate a large portion of the hot rocks in the area, but it is also likely to eliminate a large portion of the small and marginal signals given off by gold targets. This procedure may work well in areas containing just large nuggets. However, most areas I am aware of have dozens or hundreds of smaller pieces of gold for every larger piece that you will find.

Since cold rocks are made up of a lesser-concentration of iron than the average material which your detector is balanced to, they give off a negative reading signal on your detector. Ground-balancing over a cold rock will cause your detector to react positively to the average ground within the vicinity.

PRODUCTION

Once you find a location which is producing gold targets, you will want to thoroughly work the entire area. This is commonly accomplished by carefully gridding the site. By this, I mean creating parallel crisscross lines on the ground, usually about four feet apart. You can do this by drawing light lines in the sand with a stick. Grid lines allow you to keep track of where you are, and what has already been searched.

If there are obstructions in the producing area (“nugget patch”), they should be moved or rolled out of the way if possible. The smaller rocks and materials on the ground can be raked out of the way. This allows you to keep the coil closer to the ground. In a proven area, this will surely mean more recovered gold targets.

Some areas produce quite well on the surface. Then, by raking or shoveling several inches off the surface and scanning again, sometimes you can find even more targets. I know of numerous small-scale mining operations in many different parts of the world, using metal detectors as the only recovery system. They use a bulldozer to scrape away material which has already been scanned, two or three inches at a time. A layer is removed; the area is scanned thoroughly with metal detectors to locate all of the exposed gold targets. Then, another layer is removed and scanned. This process is done all the way to bedrock. They make good money at it!

I have heard of others doing the same process on a smaller-scale by attaching plow blades to four-wheel drive vehicles. Some even do it using ATV’s!

While hunting over a proven nugget patch, be sure to keep your detector properly tuned all the time. Otherwise, you will certainly miss gold targets.

PROSPECTING OLD HYDRAULIC MINING AREAS

Perhaps the most productive areas of all to prospect with metal detectors are areas which were already mined by the old-timers using hydraulic methods. Many of these areas are left with a large amount of bedrock exposed. This allows immediate and easy access for search coils to get close to old gold traps. Sometimes, the exposed bedrock has been further-deteriorated because of direct exposure to the elements. Once a nugget patch is located, raking away decomposed bedrock sometimes can produce remarkable results.

While searching such areas, pay attention to the color of dirt which covers and surrounds nugget patch. You might discover a pattern. In our area of operation, it is a white powder which often signifies the possible presence of a good spot. Perhaps in other areas, it might also be this white powder, or something else.

PROSPECTING OLD MINING TAILINGS

It is usually possible to find piles and piles of old mining tailings throughout most proven gold-bearing country.

Many of the larger earlier gold mining operations (the ones that were set up to move large volumes of material), concentrated on recovering only the fine and medium-sized values from the material being processed. This meant that the larger material was classified-out so the smaller material could be processed through controlled, slower-moving recovery systems. On the larger operations, classification was usually done either with mechanical vibrating classification screens, or with the use of a “trommel.” A trommel is a large circular screening classifier which rotates and tumbles material through, allowing the smaller classification of materials to pass through the outer screen and into a channel which directs them to the recovery system. The larger materials are passed down the inside of the trommel to be discarded as tailings.

In many of the larger operations, there were no means to recover the larger pieces of gold which were screened-out along with the other large materials. As a result, larger nuggets were sometimes discarded along with the waste material as tailings.

Anywhere you see large tailings piles, especially near the present waterways, it is evidence of a large volume operation where it is possible that the nuggets were discarded with the waste and are likely to still be there. Some large tailing piles still have large goodies inside them, which sing out very nicely on the proper metal detectors. One way to distinguish the right kind of tailing pile to be looking through is there should be a pretty wide range of material sizes in the tailing pile. Tailing piles which consist only of the larger rocks (cobble piles) were most likely stacked there by hand during a smaller surface-type operation.

Scanning tailing piles with a metal detector is proving to be highly-productive in some cases, and should not be overlooked as a possibility for finding nice specimen-sized gold nuggets. VLF ground-cancelling detectors are usually best-suited for this, because tailings almost always also contain a large quantity of mineral content, which is likely to cause interference on a BFO-detector.

PROSPECTING OLD MINING SHAFTS

Even the most experienced cave explorers shy away from entering declining mine shafts because of the dangers involved.

CAUTION: The first thing to say about prospecting in old mine shafts is that they are dangerous! There are different things that can go wrong when prospecting around in such places, one main danger being a potential cave-in. The shoring beams in some of these old shafts may have become rotten and faulty over the years. So it is best not to lean up against or bump any of the old wooden structures situated in old mine shafts. Loud, sharp noises should also be avoided.

Shafts which extend down into the earth on a declining angle are particularly dangerous; because if the ladders or suspension systems are faulty and collapse while you are down inside, you may not have any way to get out again. It is never a bad idea to bring along a caving rope, and use it, when exploring declining-type old mine shafts. Caving rope is different than mountaineering rope in that it is made not to stretch nearly as much. But I suppose, when going down in dark holes, any rope is better than no rope at all!

Another potential danger involved with exploring old mine shafts is encountering poisonous or explosive gasses. Entire mines were shut down because of such gasses—even when they were good-producing mines. These, however, were usually caved in and closed off to prevent unsuspecting adventurers from entering at a later date and getting into trouble.

Before you enter any old mine and start sorting through its low-grade ore piles, or pecking samples off the walls of the mine, it is a good idea to make sure the mine is not already owned by someone else. Or, if somebody does own it, it is wise to get the person’s permission first. There is probably nothing more dangerous in a mine shaft, cave-ins and poisonous gases included, than some old cantankerous miner who catches you, uninvited, in his mine and thinks you are stealing his gold!

There is probably more danger in prospecting old shafts than in any other gold prospecting activity.

After all that, just in case I have not succeeded in scaring you out of the idea of entering old mine shafts in your prospecting adventures, here are a few pointers about how and where you might find some rich ore deposits, or rich ore specimens, with the use of your metal detector:

But first, let me recommend that if you do go into such places, you bring along a buddy and leave another one at the surface with explicit instructions to not enter the shaft under any circumstances, but to go get help in the event that you should get into trouble within. It is also a good idea to let a few others know where you are going, just in case your outside-man doesn’t follow orders and you all become trapped inside.

There are two main sources of possible gold and silver in an old mine:

1) High-grade ore specimens that may have been placed in the low-grade ore piles and left as waste material.

2) High-grade ore which has yet to be mined.

With the exception of the largest production hardrock mines, there is always a certain amount of rock (ore) which has been blasted away from the wall of the tunnel that was not milled and processed. This was because some ore is of such apparent low-grade value that it is not worth the expense to process.

Sometimes the vein being followed into the mountainside was not as wide as the tunnel needed to be in order to progress into the mountain. Therefore, that rock material which was not part of the vein itself, or the contact zone, that looked to be of lower-grade value, was also discarded into the waste piles.

Crushing and milling ore is, and always has been, somewhat of a timely and expensive process. For this reason, a good many mines only processed what appeared to be the highest-grade ore that was blasted from the ore body. The rest was usually piled out of production’s way inside or outside of the shafts.

In the smaller operations, the kind where the ore was crushed and milled by hand and then processed with a gold pan to recover the values, only the highest of high-grade ores could be processed at a profit. The rest was usually laid aside out of the way.

The sorting of a higher-grade ore from lower-grade ore has always been a matter of judgment on the part of the person who was doing that part of the job. And, until the more recent breakthroughs in electronic detecting equipment, sorting needed to be done by eye or by feel (weight). There simply was no other way.

The interior of mine tunnels was often poorly lit with miner’s candles during earlier days, and the air inside the shaft was often foul after the powder explosions used to blast ore from the interior of the mountain. As a result of all this, it is not difficult to imagine that some higher-grade ore was likely discarded as waste material in most mines.

How rich the ore was in a mine will have a lot of bearing on whether or not a present-day prospector will find high-grade ore in the waste piles of that mine. The size of a mine does not necessarily have anything to do with how high-grade its ore was, although it may have a bearing upon how much waste ore will be available to test.

County reports can be looked over to locate the old mines within an area. Many of these reports also include information about the grade of ore being extracted from some of the mines.

When you are testing ore samples from a mine with a metal detector, and you do not come up with any specimens, try a few different piles. If you still do not come up with any specimens, it was probably not a high-grade mine. Try another.

Keep in mind that the floor of a mine shaft is likely to have some iron, brass and other metallic objects which will cause your detector to read-out.

One of the fastest and most effective ways of thoroughly checking out samples of ore is to lay the detector down on the ground or upon a makeshift bench with the search coil pointing upward so individual ore samples can be quickly passed by the most sensitive portion of the coil. The 3-inch diameter search coils are probably best-suited for this kind of work, because of the increased sensitivity, and because there is seldom great need for increased depth-sounding when testing ore specimens.

The most sensitive portion of the search coil is usually located near the center of the coil. It can be easily pinpointed by passing a coin back and forth across the coil while the detector is in tune, and by finding that spot where the coin causes the loudest and sharpest reading. The most sensitive area should be marked brightly with a Magic Marker so it will be easier for you to move ore samples directly past it. It is worthy to note that the top of the coil should have similar sensitivity to targets as does the bottom.

Ground-balancing would probably best be achieved by tuning to the overall ore pile. But, you may need to experiment. A lot will depend upon the grade of ore you are looking for. High-grade gold specimens will require the surrounding mineral to be cancelled out. On the other hand, sometimes high-grade ore is full of fine particles of gold which would not sound-off on a detector. In this case, the high degree of mineralization in the ore specimen might sound-out like a hot rock. Therefore, you would not want to ground-balance out high mineralization. So, depending upon the nature of the ore in a mine, you will need to use your own best judgment regarding the proper way to ground-balance.

Bring along a bucket, canvas bag or a knapsack so you will have something to carry your specimens as you find them.

Both BFO and the VLF ground-cancelling metal detectors can be successfully used to locate high-grade ore specimens. For the individual who is interested in finding a wider range of high-grade ore specimens rich enough to be worth milling on a small-scale for the gold and silver values, perhaps a BFO is the better type of metal detector to be used for the job. This is because the BFO does exceptionally well at picking up highly-mineralized ore. When you are dealing with hardrock veins, high mineralization is a good index of gold being present, especially when you are working with the ore that was blasted out of a previously-successful gold mine. Ore which contains large amounts of locked-in values or lots of fine gold that is thoroughly dispersed throughout the ore is not likely to read-out as a metal on any kind of conventional metal detector, although the high degree of mineralization which usually goes along with such ore probably will sound-out on a BFO-detector as a mineral. So the BFO-detector is handy in finding rich ores which might otherwise be undetectable.

By placing a BFO-detector on its mineral setting and keeping the pieces of ore which sound-out, you can accumulate a lot of good-paying ore. With the use of a BFO as such, the perimeters of ore piles can be scanned first to find a pile that has a lot of mineralization.

Portable rock crushers and mills and processing plants are available on the market. Perhaps by combining these with the use of a good BFO-detector to pick out the highly-mineralized, discarded ore, a small operation could be quite profitable without having to invest the higher costs associated with developing a lode mine from scratch.

LOCATING RICH ORE DEPOSITS

When prospecting around in an old mine with a metal detector, don’t discount the idea of searching the walls of the various shafts to locate rich ore deposits which may have been overlooked by the miners who originally developed the mine. With today’s market value of gold and advanced milling techniques, a small-scale mining operation can be run profitably in ore producing about ½-ounce to the ton in gold values, or perhaps even less. Abandoned mines which will pay this well and even better are scattered all over the west. If a person were really interested in locating a lode mine that he could work at a profit, one way would be with the use of a BFO-detector to prospect the various abandoned mines within the area of his or her interest. In using the BFO to scan the walls of such mines, highly-mineralized ore deposits can be located, samples can be taken for assay, and a person could find the mines having the richer-paying ore deposits. When prospecting like this, it is a good idea to bring a can of spray paint, a pen and paper and some zip-lock bags, so samples can be accurately marked as to where they came from, along with their respective deposits being marked with the spray paint.

If you are not interested in starting up a lode mine, but are just prospecting around for a bonus, again, the VLF detector is good for looking through mineralization and detecting the richest deposits. If, however, you do locate a reading metal inside the wall of a mine shaft with a VLF detector, and you have determined that it is not some falsely-reading mineralization, it could be well worth your while to investigate further. This is because the chances are pretty good that you have located some bonanza paying ore. I know of one highly successful high-grade gold mine in the Mother Lode area of California that is using VLF detectors as its sole method of determining where to blast. At this writing, they have located and recovered millions of dollars in gold during the past two years, in a mine which was failing prior to the use of metal detectors.

MEDICAL

Bring along some mosquito repellent during electronic prospecting ventures. Otherwise, if bugs are around, sometimes it is difficult to put your full attention on listening to what your detector is trying to tell you.

In some areas, you also have to be careful of ticks. Some ticks carry Lyme disease. Some insect repellents will keep ticks off of you. DEEP WOODS, TECNU 10-HR INSECT REPELLENT, and OFF seems to work pretty well. Spread the repellent on your boots, pants and other clothing.

In the hot climates, you should bring along the proper sunscreen and apply it to exposed body parts.

It’s always a good idea to bring along a good first aid kit, and at least leave it in your vehicle in case of emergencies.

Extra clothing and water is also a good idea. You can leave it in your vehicle. You never know…

 

By Dave McCracken

“Dredging for Diamonds and Gold During the Rainy Season…”

Dave Mack

 

Author’s note: This story is dedicated to Alan Norton (“Alley”), the lead underwater mining specialist who participated in this project. Under near-impossible conditions, Alan made half of the key dives which enabled us to make this a very successful venture.
There are very few people I know, if any, with more courage, dedication and enthusiasm to successfully complete a difficult mission, than Alan.

If I can make it go right, I try and go overseas at least once or twice a year, usually during our winter months in California, to participate in some kind of a gold mining or treasure hunting adventure. Sometimes I am paid as a consultant to do preliminary evaluations for other companies. Sometimes I just go on my own. Doing these projects in remote and exotic locations is kind of like going back into time, or like going into a different universe. It is always a great adventure! Sometimes, on these different projects, everything goes smooth and easy. Sometimes we uncover fantastic riches. Sometimes we find nothing at all of great value. And, once in awhile, conditions are extraordinarily terrible and put all of our capability and courage to the final test. Such was the case on our recent testing project into the deep, dangerous jungles of southern Venezuela.

Venezuela lies on the north coast of South America along the Caribbean Sea. It is a South American country that ranks as one of the world’s leading producers and exporters of petroleum. Before its petroleum industry began to boom during the 1920’s, Venezuela was one of the poorer countries in South America. The economy was based on agricultural products, such as cocoa and coffee. Since the 1920’s, however, Venezuela has become one of the wealthiest and most rapidly changing countries on the continent. Income from petroleum exports has enabled Venezuela to carry out huge industrial development and modernization programs.

Columbus was the first European explorer to reach Venezuela. In 1498, Columbus landed on the Paria Peninsula. In 1498 and 1499, the Spanish explored most of the Caribbean coast of South America, and Spanish settlers were soon to follow the explorers.*

Almost all Venezuelans speak Spanish, the country’s official language. Indians in remote areas speak various tribal languages.*

I personally was contacted by an American investment group that was in partnership with a Venezuelan mining company. They hired me to spend around thirty days doing a preliminary testing evaluation on a concession (mining property) the company owns in the deep jungles of southern Venezuela. The property was reported to contain volume-amounts of gold and gem-quality diamonds. A river flows across the concession for approximately twenty-five miles.

The company had purchased a 6-inch dredge along with the support equipment. They wanted me to complete a dredge sampling program to see what kind of recovery we could obtain from the river. I brought one other experienced dredger along by the name of Alan Norton. Alan and I had spent several seasons dredging together on the Klamath River in northern California, and I had learned years ago to always bring at least one very capable teammate along when doing diving operations in the jungle environment. This proved to be a really wise decision!

We flew into Caracas, which is the capital of Venezuela, a very nice, modern city with big office buildings and hotels creating a beautiful skyline. Caracas enjoys the reputation of having one of the best night-lives in the world. Poverty is also visible along the outskirts of the city where thousands of people live in small shacks called Ranchos.

The company put us up in the Caracas Hilton where we spent a comfortable night, only to fly out the following morning to Ciudad Bolivar–which is a fairly large city, and the diamond capital of Venezuela.

Upon arriving in Ciudad Bolivar, we were promptly met by representatives of the company, along with the company’s bush boss, an American adventurer by the name of Sam Speerstra. Sam would make a good match for Indiana Jones. It was quickly apparent that he loved danger by the way he drove us through traffic to the small landing strip that we were to shortly depart from on our way to the concession. Sam had us unpack our bags while he arranged to have the aircraft pushed out onto the runway by a half dozen or so airport workers.

The dual engine aircraft was not in the best state of repair. The engine shrouds were held on with bailing wire, some of the cargo doors were held together with duct tape, and the instrument panel was held in place with safety pins, some which were not holding very well.

Sam enjoyed my apprehensive observations of the plane while our baggage was being loaded. Proudly, he told me the aircraft company we were using had the best record of non-accidents in the whole country. However, he also said the landing strip on the concession was quite small and hard to get into because of a large hill that had to be dropped over quickly in order to touch down at the beginning of the runway. In fact, he informed me the company had lost one of its planes trying to land on the concession during the week before. I asked if anyone was hurt. “All dead,” Sam responded, with a smile on his face. And he was serious! .

While, for proprietary reasons, I am not able to divulge the exact location where we were operating, I can say that we were at least several hundred miles into the jungle south of Ciudad Bolivar, towards the Brazilian border.

In this instance, we were asked to do this preliminary evaluation just as the rainy season was getting started. Shortly after taking off in the dual engine plane, we began seeing large rolling clouds. The further south we flew; the larger and more dense the clouds became.

About halfway to our destination, the pilot put down on a small landing strip in a relatively small village to pick up a full load of mining equipment which he had to leave there the day before. He had not been able to get out to the concession because of the almost zero visibility caused by the heavy rains and clouds. As we landed on this strip, the first thing we noticed was a completely wrecked plane that had crashed there. This added to our apprehension and to Sam’s sense of adventure.

It took about an hour to pack the airplane completely full of mining equipment. Since we had to remove the seats to make room for gear, Alley and I were directed to lay up on top of the gear that was stacked up in the belly of the plane. No seat belts! And the plane was loaded so heavily, even the pilot was not sure whether or not we were going to make it off the runway when we took off. We barely made it, and the plane was very sluggish to fly for the remainder of that trip.

We were in and out of clouds for the remainder of the flight, much of the time with zero visibility outside of the airplane. Occasionally, we would break through the clouds and see nothing but dense jungle below us as far as the eye could see in any direction. This was the Amazon! Sam took the time to educate us on the many different types of animals and insects which would certainly devour us if we were to have the bad fortune of crashing. Tigers and jaguars, driven out of some areas by villagers, only to be more hungry and ferocious in other areas. Six-foot long electric eels, called Trembladores by the natives, capable of electrocuting a man with 440 volts, and man-eating piranha were all through the rivers and streams, according to Sam. He told us of bushmaster snakes, the most dreaded vipers in all of South America. Sam said he personally had seen them up to twelve feet in length with a head about the size of a football. “Very aggressive–they have been known to chase a man down.” Sam said you could see the venom squirting out of the fangs even as the snake started to make a strike– one of the most horrifying experiences he had ever seen. “But, not to worry, I brought along a shotgun just in case we get in trouble,” Sam told us as hundreds of miles of jungle passed beneath us.

After quite some time, at a point when the clouds cleared away just long enough to see, Sam pointed down to a short runway cut out of the jungle. At first, we could not believe we truly were going to try and land there. Sure enough, it was the base camp for the concession. We made one low pass over it. The base camp looked large and well equipped. There was also a small local village right near the base camp. The landing strip was filled with puddles and looked to be mostly mud. Alley and I were a little nervous after Sam’s big buildup, and we had very good reason to be nervous.

In order to land on the strip properly, the pilot had to fly just over the treetops, around a ridge, to drop quickly over a hill almost into a dive to get low enough, fast enough, to meet the beginning of the runway. The pilot’s skill was very good, although it is the only time in my life I have ever been in a plane that actually tapped the tops of trees as it was going in for a landing. The thump, thump of the trees hitting the wheels of the plane put me in somewhat of a panic. But it was all for nothing, because within seconds we were safely down on the runway. The pilot and Sam seemed to think nothing of the hair-raising landing experience. Alley and I felt like cheering that we were still alive. This was the mental state we were in when we arrived in the jungle. And it was just the beginning!

Local villagers came out to help us unload the plane. They all seemed like very nice people. After having a chance to load our gear into the bungalow, Sam gave us a short tour of the base camp. The whole area was fenced in. There were numerous screened-in bungalows for the various crew member sleeping quarters, a large kitchen, an office, and a large screened-in workshop area. The company had spent a lot of money getting it all set up. There was a jeep and two off-road motorcycles—all in a poor state of repair. They operated, but without any brakes.

After we had a chance to relax a bit, Sam insisted we go meet the “Capitan,” who was the chief of the local village. We had to arrange for several boats and a small group of local Indians to support our operation along the river. Sam explained to us that public relations were very important and that we must go over and have a friendly drink with the Capitan. We assumed Sam was bringing the Capitan a bottle of Scotch or Brandy or something as a gift. But that’s not the way it happened. Sam preferred to drink the local mild alcoholic beverage called Cochili. This drink is made by the local Indians from squeezing the juice out of a special plant that they grow. The juice is allowed to ferment in the open air for several days or weeks, depending upon the weather. It is a milky white-like substance with clumps of bread-like soggy goo (kind of like pollywog eggs), along with some greenish-brown mold mixed in–it was great to behold! It smelled almost as bad as it looked.

We met the chief, who looked totally wasted on something–probably the Cochili drink. And immediately upon our arrival, the chief ordered some children to bring glasses and drink for everyone. Promptly, our glasses were filled to the rims. Sam quickly downed his first glass, licked his lips, smiled and said, “This is all in the name of good local public relations!” To be polite, I downed half my glass and did my best to choke back my gag. The stuff tasted terrible! I realized my mistake right away when one of the kids immediately took my glass and refilled it to the brim. Alley was paying close attention and slowly sipped his drink, and I followed suit. There was no place to spit if out without being seen, so we had to drink it down. Sam put down three or four more glasses and shortly was slurring his Spanish in final negotiations with the chief. I’m not really sure they understood each other concerning any of the details, but everyone seemed happy with the negotiation.

It was a good thing that the rainy season prevented the remainder of our mining equipment to arrive in the jungle for the next two days. Because I spent the next few days with a severe case of the jungle blues. I was popping Lomotil tablets left and right to try and dry up my system and finally started making progress on the third day in the jungle. Man was I sick!

Alan boasted that he never had a case of diarrhea in his life and that he never would. Sam spent several hours every evening drinking Cochili with the local Indians who would accompany us into the jungle. He was getting to know them better.

The weather was hot and muggy, although the heavy rains had not started yet in earnest. The jungle was alive, especially at night when the jungle noises were almost deafening. It was certainly not a nice place to go for a friendly, evening hike. We were glad for the fence that surrounded the compound.

On the third day, still weak from the fever, but feeling like I should be productive at something, I decided to take a motorcycle ride on the new jeep trail which had recently been hand-cut several miles to the river. Why is it that I always know when I am going to come upon a nasty snake just an instant before I see it? As I rounded the first corner on the trail, a large viper took off ahead of me up the trail faster than a man could run. No brakes! Finally, I stopped the bike, turned around, and returned to camp to rest up some more.

“Once the rains started, the water was so muddy we had zero visibility underwater and had to find our way through the broken branches of submerged trees by feel”

The remainder of our gear finally arrived on the following day. We assembled everything to make sure it was all there. It wasn’t. We were missing the assembly bolts for the six-inch dredge; we had only one weight belt; and we had no air reserve tank for the hookah system! This was not good!

We finally ended up using bailing wire to hold the dredge together, and had to settle for hooking the airline directly to the dredge’s air compressor. One weight belt was all we were going to get—not much margin for error! The entire operation would depend upon us not losing that single weight belt.

On the following day, all the equipment was packed to the river by the local villagers. This was not an easy two-mile pack, because the trail was very muddy and was quite steep up and down the whole distance. Alan and I were using one of the motorcycles to get up and down the trail, which was a real adventure with no brakes.

One very interesting thing about this jungle is that huge trees, for no apparent reason at all, come crashing down. At least several times a day, we would hear huge trees crashing down in a deafening roar. On one occasion, Alan and I were returning to base camp on the jeep trail. We had just come up that trail fifteen minutes before. As we were going down a muddy hill and rounding a bend, we ran smack right into a huge tree which had just fallen across the trail. Good thing I was driving! We smashed into the tree with both of us flying off the bike. Luckily, neither of us were hurt more than just a few bumps and bruises, although the front-end of the motorcycle was damaged. Chalk up one more for the jungle.

During the time while equipment was being transferred to the river and set up, we took several airplane rides to survey the section of river which we were planning to sample, and to make arrangements at a small village (with a landing strip) about twenty-five miles downstream to obtain fuel and some basic supplies as needed during our sampling trip. Once we started, we would not be in contact with the base camp until our sampling project was complete–which was to be about twenty-five to thirty days later. In flying around the area and landing on the two strips, it soon became apparent that the pilot was very skilled. While he definitely was flying by the seat of his pants, the conditions were normal and it was no big thing (to him). Sam just had the advantage of prior experiences at the concession and was psyching us out–all in fun. It only took a little while to catch onto his game.

One of the things we quickly learned in the South American jungle, is that you never stand still for more than just a few seconds. Otherwise, a steady line of ants, mites, and other meat-eating critters will crawl up your legs, inside or outside your pants, and go to work on you. We had plenty of mite bites–which hurt, itch, and generally drive you crazy for about five or six days before they start healing. And, we learned to never brush up against bushes as long as we could help it, for fear of getting fire ants all over us. They sting like crazy!

We never allowed our bare skin (especially bare feet) to come in contact with the bare ground in or around the camps. This is because of chiggers. Ants were everywhere. Whole armies of big ants could be seen to follow a single file line up and down the trail for a mile or more, carrying torn up leaves from a tree which was actively being stripped clean by other ants. The whole jungle was crawling with life. Every square inch had some creature that was starving to take a good bite out of us. Perhaps it was the muggy weather, or maybe weakness from the jungle fever, but my first impression of the South American jungle was that it was doing everything it could to suck the life energy out of my body.

On more than one occasion, some huge animal would go crashing through the jungle just a short distance from where we were standing. We never saw the animals, but had the continuous feeling that some huge cat or wild boar was ready to come smashing in on us. And, of course, the shotgun was never in my own hands when this occurred, which was probably a good thing for everyone else in the vicinity.

“We allowed the natives to swim in the river first to make sure there were not going to be problems with piranha and Trembladores”

While we were packing gear, one of the village-helpers came running in to show off a bird spider he had caught and skewered on the end of his machete. This spider was bigger than my hand; it looked like a huge tarantula. According to the natives, these fearsome spiders catch birds to feed on, not flies, in their webs.

Our first few days on the river were absolutely, breathtakingly, exotically beautiful. The sun came out. The river was low and semi-clear. The water was warm, but just cool enough to give us satisfaction from the muggy air temperatures. We did not need wetsuits other than to protect our bodies from scrapes and bruises. We dredged a half dozen or so easy sample holes. Gravel was shallow to bedrock. The first camp was quite comfortable. The Indians were using their bows and extra long arrows to catch great-tasting fish. Everything was perfect. I remember wondering why I had such a problem adapting to the jungle in the first place. It was like paradise on the river, and we were even getting paid to be there!

We allowed the natives to swim in the river first, to make sure there were not going to be problems with piranha and Trembladores. This is not a bad thing to do. We did not make them swim first. They simply dove in. We always watch for this in a jungle environment. The local Indians know what it is safe to do. After watching the Indians swim for quite some time, we decided it was safe.

The natives live under grass roof shelters–often with no sides. They hang hammocks from the supporting roof beams and sleep at least several feet off the ground. Since Ally and I don’t sleep very well in hammocks, we brought along cots, instead. On our first night in the jungle, Sam insisted the cots would be just fine on the ground. They had short legs which put the cots about six inches off the ground. Alan and I both had sleeping bags which could be zipped up. Sam simply had one dirty white sheet. About midway through the night, Sam’s cot collapsed on him. Shortly thereafter, he was dancing around the camp yelling, “Fleas!” He was barefooted, and the natives spent the next two weeks picking chigger eggs out of the bottom of his feet with sharp pointed sticks.

Let me explain chigger eggs: These critters somehow lay eggs inside the pores of your skin. The eggs grow larger and larger, causing an open sore. It keeps getting worse until you realize it is not just a mite bite. The egg has to be removed with a sharp piece of wood, kind of like a toothpick. The eggs I saw were about the size of a soft, white BB when removed. It was explained that this was really a sack full of eggs. The trick was to get rid of them before the sack broke. Otherwise, the problem was severely compounded. Apparently, the dogs carried these chiggers all over themselves. We were instructed to not pat the dogs for this reason. It was a good lesson for us, and we learned it quickly from Sam’s experience.

We had a three hundred-foot roll of half-inch nylon rope with us for the mining operation. The following day, Alley and I allocated one hundred and fifty feet of that rope to be used to tie our cots up into the shelter beams to keep us well away from the ground. Our Indian guides were quite amused by this. The rest of the rope was used in the dredging operation.

On about the fourth day on the river, Sam returned to the base camp to supervise the other surface digging testing operations. Our cook became extremely angry soon after Sam left. I later found out that he was contracted by Sam to spend only five days in the jungle. Sam left without taking him along. He was stuck with us in the jungle for the next twenty days or so, and we all paid for his anger in the food he prepared for us. We would get fresh-made pan-fried bread every morning that was so saturated with oil that you could squeeze the oil out of it in your hand. This, along with a can of sardines for breakfast. We got leftover bread from breakfast for lunch, along with more sardines. We also got sardines with stale bread for dinner. The cook was basically on strike. Luckily, there were plenty of banana and mango trees along the river to supplement our diet.

“It was easy to follow the tributary because it was running straight black mud”

But we had our attention on other matters. The heavy rains began on the day Sam departed. In one night, the river rose up at least fifteen feet. And it roared! Entire trees were washing downriver. It was a torrent. The water was the color of brown mud. The river rose up and spread out into the jungle, making the whole area into a huge, forested lake. There were no riverbanks to be found in most areas. Our own camp was within four feet of being washed away. We knew where the river was only because of the swift moving water. Some of the river was difficult to travel upon, because it was flowing through the treetop canopy, which was occupied here and there by huge nests of African killer bees and other hornets and varmints. It was a nightmare!

On top of that, the natives caught a hundred-pound Cayman (alligator) with a net out of one of our dredge holes where they had been fishing. It was certainly big enough to take a man’s arm off. At that point, the natives told us these animals came much larger on the river.

That was the day Alley decided to come down with his own bout of jungle fever.

Since Alley was incapacitated, I chose that day to hike back to the base camp and have a talk with Sam about the adverse diving conditions. Although we had recovered some diamonds and gold already, I was not comfortable with the recovery system for diamond recovery. I also was not excited about diving in the swollen, muddy river. I would like to get a look at what is going to eat me before I die! Even the natives, who were standing in line to dive in the clear water, absolutely refused to dive in the river once the rains started. This was definitely a very bad sign. Sam managed to get the big boss on the radio and I explained the problems to him. In turn, he told me that his entire company was depending upon the results of my sampling project to justify further investment in the project once the rainy season tapered off. “It all depends on you, Dave.” I told him we would do the best that we could.

The next day, Alan was so weak from diarrhea, that he was barely able to get out of his cot to do his duty outside of camp. I felt my own duty was to go do some sampling with the help of two natives as my tenders. Rather than dredge on the main river (which was raging), I decided to test one of the main tributaries which had the reputation of having lots of diamonds. The natives left me to keep an eye on the dredge, which was tied to the canopy of some trees at the mouth of this tributary, while they hacked a trail through the tree branches several hundred yards up this creek–which was now an endless lake out into the jungle. It took several hours for them to make the trail with their machetes. It was easy to follow the tributary because it was flowing straight, black mud, compared to the brown color of the river water.

While I was standing on the dredge waiting for the natives to finish the trail, a huge bee buzzed by my head. Within a couple minutes, there were about a dozen of these bees buzzing me. They were really mean! I had my hat off and was flailing around wildly trying to keep them away. There was no place I could go off to, to get away from them. Finally, I had to jump into the water and hide underneath the sluice box. This is where the natives found me when they returned. They were quite amused.

It took quite some time for us to drag the dredge up this tributary, because the branches were just hacked off at water level. I was looking for a place we could work off of a streambank, but eventually gave up on that idea. The water was simply too deep. I ended up throwing the suction hose over the side of the dredge, primed and started the pump, put on my seventy-pound lead weight belt and other diving gear, crawled over the side and shimmied carefully down the thirty-foot suction hose. The problem was feeling my way down through the submerged tree limbs to find bottom. There were logs and branches everywhere. I was in total darkness–complete zero visibility. Everything was done by feel, sensation and yes, fear. I finally found the bottom and estimated it to be about twenty-five feet deep by the amount of suction hose I had remaining with me on the bottom. It was scary down there!

After seeing the Cayman on the day before, I had visions of being grabbed by a huge alligator, and other visions of being grabbed by a huge python. A strong voice from inside my heart was telling me to end the dive. It was too darn dangerous! Any emergency would have me and my airline all tangled in the branches. Having to dump the weight belt would put an end to the entire program, because we only had one weight belt.

I decided that I should complete the sample after all we had gone through to get me on the bottom. This is what I was being paid to do.

As I dredged into the gravels on the bottom, by feel, I discovered more buried branches and logs. These, I simply tossed behind me just like I do with oversized rocks. I got into a pretty steady routine down there and was making good progress. But the strong picture of huge alligators and pythons was right there with me all the time. Do you know the feeling you have when watching a scary movie when you know something terrible is just about to happen? And when it happens suddenly it scares the heck out of you? This was the state I was in when something heavy jumped onto my back. I let go of the hose, turned on my back, and kicked this thing off of me like a crazy man–like I was fighting off an alligator. Then I realized it was just one of the water-logged heavy pieces of wood I had thrown behind me.

This was a terrible feeling of terror and embarrassment. I’m serious; I was so scared, I wanted to crawl right back up into my mother’s womb. I was left wondering what the heck I was doing there. Why was I doing this? It was nuts!

It is impossibly-difficult times like this, and how you manage them, that contribute to the definition of your personal character and integrity. And I freely admit that staying down there to finish the sample was one of the most difficult challenges I have ever overcome. This was a total mission-impossible situation! After a moment to get myself refocused, I turned around and finished the sample hole to bedrock. I carefully shimmied back up the suction hose, coiling my airline as I went, to make sure it was not tangled in branches. When we cleaned up the sluice boxes, we were rewarded with several gem-quality diamonds, one which was quite large and handsome.

“I let go of the hose, turned on my back, and kicked this thing off of me like a crazy man!”

When I got back to camp that night, Alan was still sick in his cot. I did not hesitate to tell him of my experience. I also told him he was doing half the diving from then on, starting the next day, with or without jungle fever!

And that’s the way it went for the next twenty days or so. We completed four samples per day, with Alan doing half of the diving. Some days, the river was so high we had to tie off on branches of trees out in the middle of the river. We would take turns watching for trees being washed down the river, and would pull each other out by the airline every time this occurred, to keep from getting snagged by the trees and dragged down river.

The diving was extremely dangerous. Each time one of us went down, we did so knowing there was a definite possibility that we would not live through it. The only other option was to give up. But, we had originally agreed to do our best to overcome the difficult conditions. That’s how we got the job in the first place. We didn’t really have any other choice. I look back on it now and can enjoy the adventure. At the time, however, it was not any fun at all. It was crazy!

The biggest problem was the lack of an air reserve tank on the dredge. Sometimes it would take as much as ten minutes to feel a way down through the submerged branches in the total darkness. We had to find a path. There was no easy, fast way to get back to the surface. Cutting the weight belt loose would probably be sure death. Not only that, but we would probably never recover the body! No reserve air tank meant almost no margin should the engine quit for any reason–which, luckily, it never did.

However, the heat from the compressor did melt the airline, causing it to blow off altogether when I was down on one dive. We run the airline around our neck and through our belt for safety. With no air reserve tank, we were able to hear the compressor working underwater by the vibrational sounds coming from the airline. I had just spent quite some time finding a path to the river bottom and started dredging gravel, when my air supply was abruptly cut off and I no longer heard the compressor noise from the airline. But the nozzle was still sucking. I stayed there for a few seconds trying to understand the problem and what to do, when suddenly my air supply returned and I heard the compressor noise again. I almost just kept on dredging, but decided after all to go up and see what had happened. When I got to the surface, Alan was holding the airline onto the compressor output with his bare hand. He got a pretty good burn out of it. An inexperienced underwater miner never would have known what to do. Alley saved my life. This is one of the reasons I seldom do these projects alone.

“He made his bow out of the core of a hardwood tree, using a machete to carve it exactly the way he wanted”

As we progressed with our sampling further down the river, the natives would move all the gear to new camps every three or four days. Some camps would be reconstructed out of already-existing structures. Other camps had to be built from scratch, using plastic sheeting for the roofing material.

Our main native guide was named Emilio. He was a real jungle man in every sense of the word. He walked with a limp because of an earlier airplane crash in which he was the sole survivor. His family hut had been hit by lightning several years before, and everyone in the hut was killed except Emilio. He was a real survivor! One night, he went hunting with our shotgun–which was only loaded with a single round of light bird shot. In the darkness of the jungle at three o’clock in the morning, Emilio snuck right up on a five-hundred pound female wild boar and shot it dead–right in the head. We had good meat for several days, and even the disgruntled cook cooperated with some excellent meals.

Emilio taught us how to hunt with bow and arrows–mainly for fish. But, he was able to bring in a few chicken-like birds on several occasions. The meat was tough and stringy, but that was probably because of the cook. He made his bow out of the core of a hardwood tree, using a machete to carve it exactly the way he wanted. The arrows were made from the same hard material, using poison from snake venom on the tips for big game hunting. The natives did not have any modem weapons whatsoever, other than the shotgun we let them use while we were there.

Even Emilio refused to dive during the rains. And, our doing so considerably raised the natives’ evaluation of our physical abilities and bravery, even if we were greenhorns in the way of the jungle.

Each Indian we met was very skilled and uncanny in jungle survival. They could tell a boat was coming up the river three hours before it arrived by hearing the change in bird sounds. You will never find a harder bunch of workers anywhere.

The canoes we used were also carved
out of the trunks of hardwood trees. A skilled native takes about six months to make a good dugout canoe, which sells for about sixty dollars. Mostly, the canoes are paddled. But the more affluent natives do have outboard motors, which make the canoes go along at a pretty good clip. The natives are very skilled at driving the

canoes over top of submerged logs and through rapids. A lot of the time the boats were loaded so heavily that there was only about a half-inch of freeboard on each side. Yet, we never swamped a boat.

The gold pans they used, called Beteas, are also carved out of huge logs. Several classifications of screens are used on top of the Beteas to classify material and screen for diamonds. The natives have a special way to quickly rotate the screens, which causes diamonds to move to the center of the screen where they are easily picked out. It is quite something to watch.

Many native miners only go after the diamonds. They know they only need to find about one or two diamonds a year to make it worth their while for the extra things they want. Otherwise, the jungle provides for all of the basic survival needs of the natives. They are quite self sufficient.

“I was running down the trail at full speed like a mad man out of control, swinging my hat about

The natives received about two dollars a day in wages and were happy to get it up until the end of our project. We wanted to extend one more week to really finish the job right. However, the natives made it clear that no amount of money could sway them from going back to harvest their gardens on time.

While we were hauling our gear along the mile and a half-long trail to the landing strip, I was swarmed by African killer bees. It was terrifying! I heard them coming from quite some distance away. It sounded like a bus coming through the jungle. First, there were only a few bees around me, then a whole bunch. In panic, I was running down the trail at full speed like a mad man out of control, swinging my hat about. Then they were gone. I put my hat back on only to get stung right on top of the head. I felt completely spent. It was time to go home.

When we returned to the base camp, we found out Sam had plenty of problems of his own. At least half his sampling crew had to be evacuated from the jungle due to an outbreak of malaria and yellow fever. When we arrived, he immediately needed our help to Griphoist the jeep out of a creek that it had crashed into. Apparently, the jeep had a problem jumping out of first gear while being driven down a hill. The lower gears needed to be used to keep the jeep from going too fast, because of the no-brakes situation. Sam was driving the jeep down a steep hill with four natives in the back. It popped out of gear and they made one mad roller-coaster ride to the bottom, only to smash right through their man-made bridge into the creek. Miraculously, no one was hurt and the jeep wasn’t wrecked. We managed to get the jeep back onto the trail and hightail it back to the base camp just as total darkness descended on the jungle. Sam looked at it as just another great adventure; just another day in the life of a jungle-man!

Our trip back from the jungle to Caracas was relatively uneventful, except that I was able to buy a nicely-cut diamond in Cuidad Bolivar for pennies on the dollar at U.S. prices. I presented this to my (ex) wife when I returned home and she was quite pleased to have it mounted on a ring.

Over all, our project was successful. We found diamonds, and we found some gold. We did exceptionally well considering the impossible conditions. The largest diamond located on the concession while we were there was over eight carats. But that came out of one of the test pits on Sam’s digging operation. We never found gravels deeper than three feet to bedrock, and there was very little oversized material to move by hand–other than submerged logs. The area would be a breeze to work in clear, slower water–like during the dry season. Everyone involved was impressed with our test results. We submitted a proposal to do a more extensive test/production project with more men and larger equipment, but internal politics within the company ultimately killed the program altogether.

I’ll say this: If we ever do go back, I guarantee it will not be during the rainy season. And we will have a cook who can find no better pleasure in life than to feed us well.

* The World Book Encyclopedia, 1987 Edition.

 

 

 

By James B. Wright

Learning to interpret sound anomalies on your metal detector.

 

Noise comes to those who would use an electronic metal detector in three different basic forms:
1) Locally generated sounds (such as motors, river rapids, people talking, etc.).

2) Equipment-generated sounds (whistles, squawks, buzzes, etc., from equipment maladjustment or defects).

3) And a third noise, which is the sound of a good piece of equipment operating the way it should.

The counter-measures which must be taken against the first two types of noises should be obvious. Kill the engine, stop the talking or wear headphones which prevent outside noises from entering the ear. And, of course, adjust the equipment properly, or have it fixed, and learn to adjust it properly.

The third type of noise is the good type. It is the noise that is created when a good instrument is set up right and working most-efficiently. This noise is a “frying” sound, kind of like rain on a quiet lake, the wind through the pines, a gentle rapid on the river or a crowd at a ball game. It is a good, clean steady hiss. On a meter, it may be a steady deflection of 25-40% of full-scale.

Unfortunately, you cannot have sensitivity without this type of noise, simply because noise is built into all physical processes and all of nature.

What is “noise” as used in this context? One good example is the sound you get from your television set when it is tuned to an unused UHF channel. This is when you see snow on the TV screen. What you are seeing and hearing is the composite of a large number of random electrical impulses, all continuously being generated by the very atoms which make up the television, as well as those which make up the earth, the atmosphere, the sun and the rest of the cosmos. This is the sound of Nature doing her thing!

So, what’s the point of all this?

When you send a signal into the ground and try to detect a response from bits of gold, or from other types of deeply-buried chunks of metal, you are usually dealing with a very weak return-signal amid a sea of pre-existing natural “noise.” The detector must identify and amplify the desired signal and try to discriminate against the unwanted noise.

This is where the user becomes a part of the detection system. Because human hearing is able to pick out signals buried in noise better than any piece of electronic gear (except for certain radar equipment which is gawdawful expensive).

Why then must we not only tolerate noise but appreciate it? Because, if your equipment is so sensitive that it will sense the intrinsic “noise” of Nature, it will sense an equally-weak signal from your target. If your detector sounds-off on hot rocks or black sands, it is alive and well and doing its job.

Your job is to learn to hear and interpret the anomalies in the noise, the “whisper” that is just slightly different, the smallest change in the pitch of tone.

This is what weeds out the expert from the rest of the pack. He (or she) is like a good sonar-man, picking out the submarine while ignoring the chatter of the whales, the fish and the other noises of the sea.