By Dave McCracken

The water flow should be just enough to keep the concentrating action going behind each riffle, yet not so much that the riffles are being swept clean.

Dave McCracken

 

As a general rule, the optimum slope-setting of a sluice is around one inch of drop per linear foot of box. This can change, depending upon the volume and velocity of water being used, and/or the average shape, size, volume or weight (specific gravity) of material that you are processing.

There is no exact formula for setting the proper water velocity through a sluice box which will work optimally under all conditions for all the different types of riffles being used today. Therefore, rather than give you a formula, I will attempt to give you an understanding of what affects the proper amount of water velocity will cause in a sluice box, and also what the affects are of too much or too little water velocity. In this way, you will be able to act from direct observation to ensure that your, or anyone else’s, sluicing device will be recovering gold to the fullest extent possible.

In setting up a sluice, if feasible, it is desirable to have enough water flow to move the material through the box as fast as you can shovel (or dredge) it in at full production speed.

Most of the riffles being used today are designed so that a concentrating-action takes place behind the riffles. By increasing or decreasing the amount of water velocity over a set of riffles, the amount of water-action behind each riffle is also increased or decreased—which has an effect on the amount of concentrating action taking place. Water velocity can be increased by either putting more water through the sluice box or by moving the same amount through faster. Optimally, the water flow is just enough to keep the concentrating action going behind each riffle, yet not so much that the riffles are being swept clean (called “boiling”) of their concentrated material.

How much water velocity is directed over the box directly affects how much material will stay behind the riffles. When the correct amount of water force is being put through a sluice, its riffles will run about half full of material, and the material can be seen to be dancing and vibrating behind the riffles (concentrating) when the water is flowing.

If too little flow of water is directed through a sluice box, not enough water force can get into the riffles and they will “pack up” with material. In this case, little or no concentrating-action will take place and gold recovery will be poor. When this happens, little or no visible vibrating action behind the riffles will be seen and material will not be moving through the box fast enough to allow you to feed the sluice at production speed without loading up the entire box.

Too much force of water through a sluice box will put too much turbulence behind the riffles. This will cause some of the heavier concentrated material to be swept out of the box.

When this happens, gold recovery will also likely suffer, because the areas located behind the riffles are not calm enough to allow some percentage of the finer pieces of gold to settle. You will notice in this case that the dancing action is occurring behind each riffle, but less material will collect behind the riffles because of the increased amount of turbulence there. When you have too much water velocity, as material is shoveled into the box, it passes through very quickly and has little time to make contact with the riffles.

All the above points remain true when adjusting to get the proper amount of water flowing over an expanded metal-riffle system. However, when using such a system, it is necessary to remember that the riffles are very short. So it does not take very much water velocity to make them concentrate properly.

This means that the size of riffles affect how much water velocity is optimum through the box, how much classification of material is necessary and how fine in size your effective gold recovery will be.

The correct amount of flow is usually found to be just enough to move the material over the box to keep up with your feed of material. Since gold is around 6 times heavier than the average material that will pass through a sluice, there is usually some margin for error if velocity is a little faster than necessary. But a faster flow (than necessary) will affect how fine in size your effective gold recovery will be, if fine gold is present.

Once you have your sluice box set up the way you think it ought to be, it is a good idea to run a sizable portion of gold-bearing material through the box and then pan some samples of the tailings. If you do not find any gold in the tailings, you are set up properly. If you are finding gold in the tailings, some changes are in order. Another test is to mix some pieces of lead in with some material, run it through the sluice, and see where the lead stops.

Sluice boxes process material best when receiving it from a steady feed. Too much material dumped at once into a sluice box has a tendency to overload the riffles and choke off the concentrating-action behind the riffles. This will cause gold to wash right through the sluice box as if there were no riffles present at all.

On the other hand, it is not good practice to run volume-amounts of water flow over a sluice box without some material being constantly or regularly fed through. This is because the scouring-action from the water flows will continue to further-concentrate materials trapped behind the riffles, causing heavier materials to be washed out of the box. A sluice box operated for extended periods with no new material being fed to it has an increased chance of losing some of its fine gold values. How much gold loss will depend on a multitude of factors, such as the type of riffle design, how much water flow, the type and weight of concentrates and the size and purity (specific gravity) of the gold.

So if you will not feed more material into your sluice for a while, it is a good idea to cut your water flow back to reduce turbulence behind the riffles until you are ready to feed again.

Even when a sluice box is set properly, occasional larger-sized stones or rocks can become lodged within the riffles. These should be picked or flipped out of the riffles with minimum disturbance to the remaining portion of the sluice.

On most suction dredges, the volume of water being moved through the sluice continues at the same steady flow during production speed. So adjusting the water velocity to set up the dredge right is accomplished by changing the slope of the sluice box itself—which will speed up or slow down the flow of water over the box. Then, once you are dredging, if you will stop feeding streambed material into the suction nozzle for any period of time, it is wise to block the nozzle with a larger-sized cobble to slow the water flow through your sluice box.

When placing a sluice box within a stream or creek for its water flow, the water velocity can be adjusted by either changing the slope of the box, by varying the volume of water being directed through the box, or by placing the sluice at different sites in the stream or creek where the water is moving at different depths and speeds. Getting the right flow of water to pass through a sluice box out in the field is not difficult. But it is sometimes necessary to try different ideas until you find what works best in each situation. For example, in a location where the water is moving slowly, you might be able to direct more water through the sluice and gain the amount of water velocity that you need. In a stream where the flow is moving more swiftly, the water velocity through your box can usually be adjusted by changing the volume of water directed into it, and/or by varying its downward slope.

Usually, you will have little trouble arriving at the correct velocity through your sluice box when placing it in a fast stream of water. You can use river rocks to make a foundation within the stream so your box can sit level from side to side. By allowing different amounts of water volume through the box, and by changing its downward slope, you can work out a combination that does the job. It is good to have a length of nylon cord along with you for securing the sluice box to a rock or some other object upstream. This prevents the box from being moved off its foundation by the force of water. Sometimes it is necessary to pile a rock or two on top of the box to hold it in place. This is especially true when you are using a sluice made out of wood. You can shovel gravel into the box while trying the different combinations to see what effects the changes have on water velocity.

In a situation where you must set your sluice into slower water, you will find it is generally more difficult to get the flow you need, because you have to create more water velocity than is presently there.

If the flow of the stream itself is not enough to move material through your box, you will sometimes find that changing the slope of the box within the stream has little or no effect on speeding up the flow through the sluice. In this situation, there are several things that might be done to channel enough flow through your box so that you can run material through at production speed. Sometimes the flow of water within the overall stream itself is enough, so that by setting up a “water director” in the stream, you can move enough water through the box to give you the desired result. A water deflector, or barrier, like this can sometimes be built by throwing river rocks out into the stream to make more water flow into and through the sluice.

In this situation, there are several things that might be done to channel enough flow through your box so that you can run material through at production speed. Sometimes the flow of water within the overall stream itself is enough, so that by setting up a “water director” in the stream, you can move enough water through the box to give you the desired result. A water deflector, or barrier, like this can sometimes be built by throwing river rocks out into the stream to make more water flow into and through the sluice.

Sometimes you can get the water velocity needed by arranging a small water-elevator across the waterway. By doing so, and by placing your sluice where the moving water spills over the top, you might create more than enough water flow through the box to meet your needs. It really does not take very much volume of water through a medium-sized sluice box to get the right amount of velocity, if the water is moved through the box at speed. In the case of a short elevator (dam), the water level might only need to be raised up slightly to increase the downward slope of the box enough to create the needed water velocity. How high the elevator needs to be depends mostly upon how much water is flowing within the stream or creek.

A sheet or two of thin plastic, or a plastic tarp, or some old rice bags, can come in handy when you are arranging an elevator or water director within a stream. Such material helps prevent the water from pouring through the holes in your man-made barriers.

A water director or elevator can most often be used with good result wherever the water in a stream or creek is moving and is shallow enough that the barriers can be built easily.

If the water at the work site is moving too slowly, or for some reason a water director or elevator will not work in a particular location, it will be necessary to either set up your sluice in a different location where the water is moving faster, or use a motorized pump to feed water into your sluice. Or, in some situations, it is possible to siphon water into your box from a higher point upstream. Siphoning can be done effectively with the use of reinforced garden hose(es), other types of heavy-walled water hose or PVC.

 

 

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)

 

 
video subscription graphic
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 STEVE HICKS

Placer miners at work

Placer mining is relatively simple as long as you don’t expect to make a profit; but it becomes much more difficult if your intention is to make some money. If you want to make some money, it’s a lot easier and cheaper to learn from other people’s mistakes, than to put yourself through the school of hard knocks. By far, the most common mistake I see is inadequate or improper sampling, which is often due to gold fever. Other mistakes are: not properly cleaning up bedrock, not researching the past mining history of your area, and starting a mining venture under-funded.

Placer miners diggingFirst, we will cover sampling. A common remark I hear is why put the time, effort, money, etc. into sampling when it can be better-spent on actual mining and making some money? All too often, individuals lose thousands of dollars on their mining ventures; but had they done some sampling and found out that the ground was too low-grade to mine profitably, they would have only spent hundreds of dollars. I have seen an individual go broke trying to mine ground containing less than $2 of gold per yard when there was un-mined ground about 300 yards away running slightly over $100 per yard. That is not a typographical error; it is one hundred dollars. This is, of course, an extreme example; but all too often rich ground is missed. Even before sampling, a literature-search is in order to get an idea of the ground’s value.

Another common mistake is not separating overburden from pay gravels. Novice miners frequently like to run low-grade overburden. This is because the more gravel they mine, the more gold they recover. While mining everything on a property will maximize the amount of recovered gold, it could bankrupt a person at the same time. If the overburden only contains $2 of gold per yard, and your mining cost is $5 per yard, then you are losing $3 for every yard put through the wash plant.

On the other hand, if you can strip low-grade overburden for $1 per yard, then you have saved $2 per yard which can be directed toward mining the pay gravels.

Gold sample in panOften, new miners leave a lot of gold values in the bedrock. Some highly-fractured bedrock may have values several feet below the surface. The deepest I have ever read about was a Canadian mine going down nine feet into bedrock to get all of the values.

Most often, the bedrock values will be in the top two feet of bedrock. Once you mine the top six inches, check the next six inches to see if there are still enough values to make it pay. Once again, you must evaluate your mining costs for ripping up bedrock to determine if the effort will pay adequate dividends.

Starting a placer operation under-funded is another common mistake of novice miners. It is a mistake to count on finding some profitable ground to pay off debts right away and carry you through the rest of the season. Unforeseen problems have a way of cropping up, such as equipment breakdowns or a severe water shortage later in the season.

Even though most individuals reading this article won’t be running a large-scale mining operation, these tips should help you toward a more profitable operation even on a smaller-scale. Maybe, with some increased sampling or more efficient mining, you just may find that big nugget this season!

About the Author: Steve Hicks is a geologist specializing in sampling gold placers. He has previously worked a number of years as a mineral examiner for the BLM in Alaska and Montana. Presently he is doing placer consulting work and residing in Livingston, Montana.

 

BY DAVID KAREJWA

 

 

Dredging is very hard and tedious work at its best. The more we dredge, the more we realize how much time is actually spent moving oversized material out of the way.

Some pay-streaks don’t have any large boulders at all. Then again, some pay-streaks have an abundance of boulders—many of which are too large to move by hand. When this is the case, gold production results no longer depend on how well you can operate a suction nozzle; they depend on how efficiently the boulders can be moved out of the way.

Many of us started by using two-ton come-alongs to pull the boulders out of the way. And while this may work fine on a very small-scale operation, or an operation which only runs across an occasional boulder, it does not work well at all on a commercial scale.

Pay-streaks can be time and energy-consuming to find in the first place. Being ineffective at moving the boulders out of the way can greatly lessen a dredger’s ability to succeed. I have been dredging on a somewhat serious level on the Klamath River during the past four or five years along with a number of other serious dredgers. Together, we have innovated new boulder-pulling equipment concepts which have improved our sampling and production capabilities to an enormous degree.

The most comprehensive demonstration of underwater dredging I have ever seen is contained in Dave McCracken’s video, ” Advanced Dredging and Sampling Techniques.” Detailed winching and rigging techniques are also fully laid out with diagrams in Dave’s book, “Advanced Dredging, Volume 2.” These are highly recommended for those of you who will get serious about winching.

We found that a winch can be mounted on a floating platform, and the platform can be anchored out in the river behind our dredge hole. We use an electric winch in most cases, but new designs are including hydraulic winches.

The platform is anchored to the rear—either by cabling it to a boulder or a tree on the bank, a boulder or a group of boulders in the river, or to a dead-man placed in the river with tailings from the dredge dumped on top to anchor it.

The winch cable and boulder-harness extends down into the dredge hole. Also, the winch controls, on a cable, are waterproofed, and extend down into the dredge hole. When a boulder needs to be winched out of the hole, it is just a matter of slinging it, and winching it back, with all of the winch controls directly at your fingertips. This greatly improves the situation over having to put an additional person up on the bank to operate the controls of a mechanical winch, having to give signals, etc. It allows for single-person operations. While I don’t advocate people dredging alone, a lot of people do. If you are one of them, with this system, you are able to dredge for awhile; and when a boulder needs to be winched, you can simply sling it and drag it out of the way—just like that.

The old way required single-dredgers to sling the boulder, then go up onto the bank to operate the winch. When the boulder got jammed against some obstruction along the river-bottom, the person would have to go back into the water, try to free it up, back to the winch, back and forth, etc., until the boulder was finally moved out of the water. It was a nightmare!

One excellent advantage to a floating winch, we have found, is that the pull is also in an upward direction on the boulder. This helps slide the boulder more easily because of less friction along the river bottom. It also helps get the boulders pulled up and over other obstacles. Consequently, there are fewer problems with the boulder being jammed up while it is being pulled.

Floating winch platforms are relatively inexpensive and easy to construct. They don’t generally need to have much more flotation and size than an average 6-inch dredge. They are not very heavy, and they are easy to float around in the river. In fact, we use the extra deck space on ours to store our extra dredging and cleanup equipment, extra gas, etc.; the things we don’t like cluttering up the decks of our dredge. We place a portable motorized electric generator on the winch platform to keep the winch battery fully charged while we are diving.

Some commercial dredgers on the Klamath River have taken this concept one step further by placing the electric or hydraulic winch on the front of their dredge platform. The dredge is directly behind the hole, anyway. This normally requires an extension of the dredge flotation platform in the front to allow for the additional necessary buoyancy. The advantage to this concept is not having to move around two separate platforms. The disadvantage is not being able to pull the boulders far enough to the rear when you are dealing with lots of boulders.

When you are winching from the front of a commercial dredge, it is also important to keep looking up to make sure you don’t pull the front of your dredge entirely underwater!

This can also potentially happen with a floating winch platform, but it is not normally a problem, because the pulling point is generally from the center of the flotation, as opposed to directly off the front of a dredge.

One local innovative dredger recently came up with the idea of mounting a winch on the front of his dredge in a backwards direction. By also mounting a snatch block under the center of his dredge, under the sluice box, then the pulling point of the winch is centered better on the dredge’s flotation platform. This helps eliminate the problem of submerging the forward part of the dredge.

One point to remember is to never tie off the rear of your dredge to a high point on the bank, or to a highline across the river, when you are planning to winch off the front of the dredge. This type of rigging will pull the back end of the dredge up into the air during rock pulling!

The biggest problem we have run into with floating winch platforms is in the electric controls. We have yet to find an underwater control box on the market which is designed for electric winches. So we have had to waterproof the standard control boxes. This is not all that difficult to do, but it is only temporary. Every few weeks, we find ourselves taking the box apart, and having to rework it.

There is also a potential safety hazard with the electric winches, in that if the controls short-out underwater, the winch can simply start winching! We have learned to create a quick disconnect on the electric cord near the control box. If we lose control of the box, we can unplug it, and the winch will shut down.

One important safety note on this: If you create a safety quick connect using extension cord plugs of some kind, make sure you put the female-side on the power cord. This way, the power cannot be shorted across once the cord has been unplugged. This lesson was learned locally the hard way when a dredger unplugged the control box and dropped the cord into his aluminum boat. He had the cord rigged with a male fitting. The male posts touched the aluminum of the boat, and he was winching!

While it is not particularly difficult to do, it is a bit involved to waterproof the control box to an electric winch—too involved to go into in this article. We use a fifty-foot #14 extension cord; we use a product called Dip-it, and we do a few other things to avoid making the modification so permanent that we cannot easily get back into it to re-do it when necessary.

The advantage to hydraulic winches is in having no problems with the control box. No electricity! This is why I believe the best future platforms will be utilizing hydraulics. For dredge platforms, it is not too difficult to mount a hydraulic pump directly to the dredge motor.

I hope this information has been of as much help to you as it has been to us dredgers up on the Klamath River.

 

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.

 

 

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