By Jude Colleen Kendrick

 

Dry washing1I remember, in my beginning days of prospecting, driving through the Upper Mojave Desert in Southern California, looking for mines to explore and tailings to scratch through. Occasionally, off to the sides of the road, I would spot small areas where dust and sand billowed up. At first, I thought that they must be “dust devils,” yet they never seemed to change position. In my imagination, I wondered if someone was sending up smoke signals, because that is what they appeared to resemble. One day, I decided to satisfy my curiosity and follow a dirt road up to the puffs of dust.

As I drove up, I saw an old man shoveling gravel into what I now know was a dry-washer. My own previous experience in gold mining had been with suction dredges, so I was excited at the possibility of another way to find gold! The gentleman was kind enough to show me how his dry-washer worked. He explained that he also dredged during the summer. But during the winter months, he headed for the more moderate desert-climates. The thought came to me that now I could prospect year-round, and that everyone in my life would really be annoyed at that. This was because I didn’t leave much time for anything else but gold prospecting, as it was!

For a more comprehensive explanation about dry-washing, please click here.

The old prospector’s machine was a “Nicks Nugget;” which, as I understand it, was constructed upon the design of an “Old Beck’s” dry-washer. It basically worked from a large bellows which was run by a small gas engine set up around 10-feet away (to separate the motor further from the dust). There was a 10-foot leather belt attached to the pulleys. I noticed that the pulleys were connected in such a way that the entire machine vibrated when the bellows opened and closed. The man told me that he would not have any dry-washer other than a Nicks Nugget I, of course, asked him where I could find one for myself. He told me, “Someone one has to die, because they are not made anymore and that’s the only way you’re ever going to buy one!” That is exactly what happened about a year later. An old prospector in the town of Randsburg passed away. I heard that his equipment was being sold and bought the Nicks Nugget!

Drywashing machineMy machine has great recovery. I have tested my tailings throughout the years; and to my knowledge, I have never lost a single speck of gold!

The desert is peaceful and quiet. At night, you can see the sky and stars in a way that is beyond words…

I should point out that dry-washing is a dirty way to prospect. No matter where you set up the machine so that the dust blows away from you, the wind figures out what you are doing. Then it changes direction so that you get a mouth-full of dust with every shovel-full of gravel! I suppose this is just one of Mother Nature’s many ways of making you pay dearly for her most cherished golden treasures!

Most of the time, I wear a bandanna, which helps a little. But when I go back to camp, I still look like “Pig-pen” from the Peanuts cartoons! Still, it has always been worth it.

Winter in the desert can be hard at times, because the temperature-changes are quite drastic. It will be a comfortable 70 or 75 degrees during the day. Then, the afternoon winds can gust up to 60 miles per hour, and the temperature can drop as low as 20-degrees during the night. I woke up one morning to find that all of my panning water was frozen solid. I could not believe it!

The desert also demands the most out of your creativity and imagination. Very often, we all forget some part of our equipment, no matter how careful we are about packing. Yet with a little thought, anything can be fixed. On one trip, I had forgotten my large panning tub, so I ended up digging a hole, lining it with a large plastic garbage bag, holding the edges down with rocks. Presto; a baby swimming pool! I used it to pan down and perform final clean-up on the concentrates from my dry-washer.

Another time, the worst possible items were forgotten; which were the legs to my dry-washer. Can you imagine? I was frantic! After a few moments of figuring my whole trip was for nothing, I looked over the poles from my picnic awning, and the light went on in my head. Shortly thereafter, I took two of the poles, broke them off at the length I needed, and punched four holes in the poles for the nuts and bolts. Within minutes, I was already cranking up the dry-washer. There is always some solution if you are in the right state of mind; you just have to find it! I’m sure this is all just a part of gold prospecting.

The beauty of the desert makes up for any discomforts which you may experience along the way. Usually, nobody is around for miles. It is peaceful and quiet. At night, you can see the sky and stars in a way that is beyond words. And the gold has always been there for me, from flour to nuggets of various sizes and shapes.

One of my favorite things to do while dry-washing is run my machine all day, collect all of the concentrates; and then at night, by lantern-light, pan everything out! There is something wonderful about working everything down to that glimmering, beautiful gold at the end of my day!

During my years of dry-washing, I have spent Christmas out in the desert a number of times. One year, I grabbed three friends (who have parents and family in other states), and took them to one of my mining claims for a “different” type of Christmas celebration. We decided we would cook our turkey on the BBQ and try to make the side dishes on the Coleman stove. A friend of mine had hooked-up an apparatus so that my rotisserie on the BBQ worked off a 12-volt battery. It was great!

My friends and I thought everything was under control until we realized we had bought too large of a turkey. So we ended up eating our Christmas turkey at 10:30 at night! By then, we had already eaten all of the side dishes as “appetizers.” After a few toasts of champagne, nobody seemed to care much about how or when the turkey was done! It was sometime during that evening that one of my friends decided to make a “snowman” out of three large round lava rocks. Even though there was no snow out there, we found ourselves making the best out of our situation. I’m certain that none of us will ever forget that Christmas experience!

Now-back to the important thing — gold! I have usually dry-wash alone; but when I do have a partner, it certainly makes things a bit easier on both of us. One person can be breaking-up the gravel while the other can shovel. During one of my trips, I ran into my friend Ed “Half-Bucket” Daugherty. So we decided to team up for a while. Later, when we realized that we were onto some good gold, he and I were both feverishly shoveling gravel into my machine so fast, that several times we crossed our shovel handles and sent gravel flying everywhere. To this day, I am convinced that it was those lost shovelfuls which had the big nuggets in them! I’ve often wondered if “Half-Bucket” ever went back out there to get them…

I once watched a young man with a whisk broom and dust pan going from one prospect hole to the next, left behind by other people. He merely swept the shelf completely clean and panned-out what he had collected. He found more gold that way than I did running yards of gravel into my dry-washer! So I started using this method, but took it a step further. I took a gas-powered vacuum, sucked up the layers left on the shelves by others, ran that material through my dry-washer, and then panned-down the concentrates. Trust me; by following this method, I have always recovered a lot of color and sometimes a small nugget or two. I nicknamed this method “dry crevicing.”

While I have not tried it yet, I have run across others in the desert who have made fantastic gold recoveries using modern metal detectors to locate pockets and “patches” of nuggets. I have this plan of trying to combine modern electronic detecting with dry-washing…

At the time of this writing, it remains a little warm to start working my mining claims in the desert. Writing about it, though, has me counting the days until the weather cools.

Until then, I’ll look at my gold from last season and imagine my bottles completely full for the next time.

But even if they aren’t full, the desert and dry-washing are wonderful for the winter months. I can’t wait! Good Luck!!

 

 

 

By Dave McCracken

Every successful gold miner will tell you he or she is absolutely willing to devote whatever time and energy is necessary to locate the next discovery!

Dave Mack

Why is it that some people are able to succeed well at gold mining on a continual basis, while others have difficulty making it work?

There are a multitude of factors which contribute to the success or failure of any operation, but there is one factor which I feel underlies all the rest. It has to do with time.

Upon close inspection, you will find that every person who is doing well in these activities, other than the occasional lucky person, has been willing to devote a great deal of time to his or her mining activities. While luck does contribute to some excellent discoveries, you will find that good luck comes around more often when you spend more time searching for gold.

Unquestionably, there are skills, techniques, and standard procedures to learn in order to succeed well in gold mining. It takes time to get through the learning curve.

People who get involved with the idea of getting rich quick are usually disappointed. People who are willing to devote whatever time is necessary to polish their skills, and who are willing to devote themselves to locating the next discovery, usually do pretty well.

And, it is not necessarily true that you need to spend a lot of time before you start making important discoveries. It is mainly the willingness to devote lots of time. We have seen many beginners, who were approaching the activity with the correct viewpoint, do very well right from the start.

Most good things in life take some time to develop. Get rich quick schemes tend to cheapen the value of an activity. More often than not, it takes time to do things the right way, to make things come out good in the end.

Older people, wise with age, often say that their most worthwhile accomplishments took lots of time and energy. And, for them, the time and energy spent was the best part of it!

There are few activities which are better, more exciting, and more rewarding than gold mining and treasure hunting. While it can be aggravating at times during the testing stages when you are not finding what you are looking for, this just makes the thrill of discovery all that much better.

Every successful gold miner will tell you he or she is absolutely willing to devote whatever time and energy is necessary to locate the next discovery. And this is a lesson we could all learn from.

 

“Shallow water dredging can be very rewarding”

 

When it comes to small-scale gold mining, disability does not mean inability. It simply means that we must make accommodations. If you want to say that you can’t do something, then you won’t be able to do it. Your disability, when it comes to mining, is a state of mind. There is a form of small-scale mining that will fit everyone.

Possibly, I have been fortunate in being able to find miners to show me how to mine. Almost everyone I have run into has been more than willing to help, but better than that, they were willing to share their knowledge with hands-on demonstrations. Using this information, I have been able to determine what accommodations I must make for my personal disabilities.

Most of us are unwilling to accept the fact that we may not be able to do something. I think those of us with disabilities may have a greater failing in this. I’m as guilty as anyone.

I started out with a pan and a couple of buckets, and then added a sluice. What I hadn’t properly learned was how to pan. With two bad shoulders and a lack of breathing capacity, the standard panning style just doesn’t work. An old miner with arthritis in his back showed me how he does it, and it works. Confidentially, I still don’t pan well, and that’s why I own a mechanical panner. The next step up was a 2 1/2-inch dredge. It breaks down into manageable loads, and I call it a “four tripper.” Four trips for me to get it in or out of an area.

Keep in mind that miners are a friendly and helpful group. If you are having trouble moving equipment, then ask for help, but I’ll bet you are offered help before you ask. Don’t let anyone kid you, shallow water dredging can be very rewarding. You may not be pulling an ounce a day, but what’s wrong with a couple pennyweight? Also don’t forget that at the end of the day you are going to have to do something with the concentrates you have produced during the day. They weigh twice as much at the end of the day when you are carrying them to your vehicle.

The biggest mistake I made was to let my desire to move more material overtake my common sense. I bought a 4-inch dredge. It became a six-plus tripper. After putting it in the water twice, being exhausted each time, and having friends become very concerned when they watched me move the loads, I have given up on that idea. I’m now back to the 2 1/2-incher. I recently saw in a magazine article a listing of what the author felt was the minimum dredge set-up to start out. He felt that a 4″ dredge was the best, and this included air. I won’t argue too much, but my concern is really with the many miners who begin using air without training. For the person with a heart or lung problem, the compressed air could be a killer.

Another alternative to consider is having a partner. It can be your wife, girlfriend, or just a friend. This way you can share the equipment-moving chores, and you can complement each other when it comes to the mining. If nothing else, someone has to carry the drink cooler and be “straw boss.”

Small-scale gold mining can be good exercise, but know your limits. Have a talk with your doctor to see if there may be a change in your medication due to exercise or altitude. My medications do change when I’m on the river. Your doctor will probably look at you like you are crazy when you say gold mining. Just show the doctor some of the gold you have found. You may end up with the Doc on the river, too!

 

BY MARCIE STUMPF/FOLEY

There is a fairly new method of mining out there in the mining community that is rapidly gaining in popularity, with good reason. It is called “Vacking;” and, as you might suppose, involves vacuuming material.

As a suction dredge vacuums material from the bottom of the river, this is a type of dry-land dredging. It involves using a small, lightweight unit to vacuum cracks and crevices of exposed bedrock, moss on exposed bedrock or boulders, or material in a dry wash in the desert. For this “dry land dredging,” however, there are no uncomfortable and expensive wet-suits to don, no heavy equipment to carry and then set up, and no long period of learning how to operate the equipment, or learning where to find gold.

Anyone who is familiar with mining knows that there is a much larger proportion of fine gold deposited than large gold, in almost any area. Each winter, as the rivers swell with winter rains and snows, much fine gold is washed down them. The fine gold, since it is much lighter in weight, is deposited much higher on the banks, or in the material of the river. As the high waters recede with the onset of spring and summer, much of the areas where the fine gold is deposited is left exposed up on the banks of the rivers.

The new units consist of a two-cycle gasoline engine mounted on a five gallon container, which is equipped with a suction hose and a crevice nozzle. They are very efficient at pulling the fine gold from moss, and at cleaning out crevices. Previous efforts to accomplish this by hand were slow and painstaking, and not very efficient. Collecting fine gold has always been one of the greatest challenges facing any miner, and some people spend years attempting to perfect their fine gold recovery.

Not only does “vacking” do an excellent job at recovering fine gold — it is a lot of fun! It is so fast, simple, and easy to use, that it seems to take all the work out of mining. You are still out in the great outdoors, still getting healthy exercise, but all that’s left when you remove the excess work is the fun.

Since we live and work very near a gold-bearing river, if my husband can squeeze two hours of time, he can get to his favorite spot, set up, get in most of that time mining; and still come home with enough gold to feel he has been mining. If he is dredging, that’s not enough time to more than set up and get started before he has to quit!

These units come on their own back-pack frame, and all accessories are carried right inside the unit. It is a completely self-contained unit, and includes an extra fuel bottle, a crevice tool, a gold pan, a “sniffer bottle” to remove the gold from the pan, and even a sample vial to keep it in. With all these accessories, the unit weighs just 15 lbs., so you could hike into the back country with it without undue strain.

Many wives who are not interested in dredging or motorized sluicing (high-banking) enjoy using this type of unit because it is something they can do completely on their own. The only problem we have seen develop is that when some of the husbands see that the gold recovery exceeds that of their dredge or motorized sluice, they want to use one also. Then, they either fight over the one unit, or join the growing group of “two-vack” families. Since they are such low-cost units, this is pretty easy to do.

I recently talked to one avid vack-miner who has been using one of these units for two years. He was concerned that he might possibly lose some of the fine gold out the exhaust as the unit filled, since it is so lightweight. Shortly after purchasing his unit, he fitted an elbow and extension over the exhaust, and directed it into a container of water. He has used it faithfully, and panned out the light powder that accumulated each time. He has never found even a speck of gold in it.

A crack or crevice in exposed bedrock that runs crossways to the current of the river acts as a natural riffle, catching fine gold just as the riffles of a sluice do. The moss that accumulates on exposed bedrock acts much as the carpet in a sluice, only better! It is amazing just how much fine gold can accumulate there. These are prime areas for vacking.

Areas where people have been working with motorized sluicing equipment have also proven to be good. Even if they have worked the area down to the bedrock, they have been unable to clean the area as thoroughly as it can be cleaned with a Vack, and generally, the richest areas are right on the bedrock.

The greatest demonstration I have ever seen about how gold traps in bedrock and moss, and how much work it is to recover it using conventional methods, is contained in Dave McCracken’s video, “Modern Gold Mining Techniquies.”

Although I have not mentioned finding nuggets with this equipment, it certainly does find them! Even areas that have predominantly fine gold in the high bedrock will trap nuggets during flood storms, and if they are there, this equipment will help you get to them as nothing else will.

Since you do not work directly in the active waterway, and this equipment does not put anything into the waterway, there are no dredge permits required for the use of these units, at least in the state of California.

All in all, Vacking has such a wide range of applications, in so many areas of the country, by such a wide range of people, that the gain in popularity is very understandable. It can only be expected to grow.

If you should get the Vacking bug, be sure you look for us out there, because that’s where we will be every chance we get!

 

By Dave McCracken

How much you need to qualify a gold deposit in advance depends upon the additional investment that will be required to gear-up for production.

Dave Mack

In placer mining, there are fundamentally two kinds of sampling:

1) Discovery: Attempting to locate a higher-grade deposit of value inside of a larger volume of lower-grade material.

2) Quantification: Extracting and analyzing smaller portions, to gain a perception of how much value exists within a larger volume.

The general concept behind sampling is to minimize investment into a specific mining property, or a particular project, until there is enough proof that a mineral deposit exists which contains enough value to justify a more substantial investment.

The kind of sampling that you should do, and how much is necessary, largely depends upon the ultimate objectives, and/or how large of an investment you will make to implement a commercial project – especially that portion of the investment which cannot be recovered and re-committed to some other project at a later time.

For example, if you are going to join The New 49’ers Prospecting Organization to gain access to 60+ miles of mineral properties in northern California, and decide to devote an extended period of time into searching for and developing high-grade gold deposits along those properties, the money you would spend outfitting yourself with a sampling dredge is something you can depreciate over the extended period. This is because the investment will not be confined to a single mining project or property. When you are done, because the dredge and gear will be accessible, you can regain some of your investment by selling the used equipment.

How much sampling would be necessary in advance of making this investment? Not so much, because most of the investment is not committed to a single mining property. Before a final decision is made, perhaps it would be worth spending a week of your time participating in a Group Mining Project, to obtain some direct exposure to the activity, and see if this is how you want to spend your time.

On the other hand, if you were considering a substantial capital investment to start up a full-scale commercial dredging program on one specific mining property out in the middle of Borneo’s rain forest, where accessibility is only available by helicopter; it would be wise to first send in a sampling-team to confirm the existence of commercial deposits that will allow you to make a reasonable return on your investment. Knowing that most of the capitalization into this kind of mining project is unlikely to be diverted to some other program at a later time, how much sampling would be enough? It should be enough to:

1) Verify that commercial deposits exist on the property; and,

2) Quantify the deposit(s) well enough to become certain that the commercial value of the project is justified.

Sampling is a careful, organized method of attempting to locate high-grade mineral deposits; and then, obtain a reasonable perception of the value they contain.

Here are a few basic sampling principles:

1) The larger the sample, the more accurately the sample results will represent the larger volume of material that has not been analyzed.

2) The more samples you take, and the closer they are together, the more accurately the average result will represent the larger volume of material that has not been analyzed.

3) To achieve an accurate result in sampling, it is vital that you thoroughly clean all of the values from sampling equipment in-between samples.

4) As mineral deposits can be found at different strata’s within a streambed, a good sampling program does not only test in different geographic locations; but also at the different layers within a streambed. This is because it can often be more commercially-productive to mine a deposit only down to a specific strata.

 

On this river in Madagascar, the gold (plentiful) was so fine, the sample material had to be dredged into a large catch basin suspended between two boats, and then processed using specialized equipment on the bank.

5) To be effective, recovery-equipment used in sampling must have the capability of concentrating the values which exist within the deposit. Where special recovery equipment is needed, and the sampling must be accomplished with portable dredging equipment, it is sometimes necessary to dredge the samples into a floating catch-container. Then the samples can be carefully processed on land.

Sizing the gold being recovered, and the gold that is not being recovered, is an important part of a sampling process.


6) Care must be taken to ensure that foreign material is not introduced into the material being sampled which can render the result inaccurate. Just as this has to do with foreign material from other geographic locations, it also has to do with material from different strata’s within the streambed, if layers are being tested independently of each other.

7) The smaller the sample being analyzed, the more the result can be thrown off by the introduction of foreign material (called “contamination.”)

8) Tailings from a sampling recovery system should be carefully analyzed to see what values are being lost; and whether steps can be taken to recover the values in a production operation.

9) Ultimately, only the values that can be recovered during production should be included in the final business projections.

10) Care must be given to measure the amount of raw volume that is excavated to extract a sample. Because the value recovered must be related back to the amount of material that was moved and/or processed to obtain the result. This relation will need to be measured against the volumes and costs associated with a potential production operation.

For example: If an average cubic meter of streambed gravel to be processed will produce $10 in gold (gold at $425/ounce), at a gross production cost of $4 per cubic meter, when a production dredge is operating at 100 cubic meters per day, you can predict a net income of $600 for each dredge participating in the program.

Sampling is generally accomplished in two steps: The first step is to locate the existence of a mineral deposit. Usually, when we use the term “preliminary sampling program,” we are talking about a project where the existence of high-grade deposits still needs to be confirmed.

The second step is to sample the deposit(s) enough to gain a perception of its value. And that’s what this article is really about; how much quantification is necessary? The answer to this question largely depends upon the additional investment that will be required to gear-up for the desired volume of production.

Where we dredge along the Klamath River in northern California, using the very same equipment and support-structure in sampling as we do in production, we do not have to do very much quantification of a deposit before launching into production. This is because just finding the high-grade is reason-enough to mine it. Although, we usually do devote several samples in an effort to find a low-grade area where we can place tailings. Then, we establish the value of the deposit as we mine it.

The reason we can do this, is that under these circumstances, there is no substantial amount of increased financial risk when we transition from sampling into production.

Local miners were recovering rich deposits in the Cambodian jungle using very primitive, low-volume methods. Here was a good place to start with a sampling dredge.

However, many situations are different from this. Some mining projects are just in the start-up phase. Some mining prospects are in remote locations. Under many circumstances, to minimize risk, it is wise to begin with portable sampling equipment to complete the preliminary sampling phase of the program.

Local miners were supporting their villages in Madagascar by digging gravel from the bottom of the river out of boats using long-handled shovels. Our sampling later proved they were digging on the strongest line of gold in the river.

In this case, the question remains how much quantification is necessary to support the evolution to the next level of operations? This will always come back to the program objectives – which often have to remain flexible, depending upon what is discovered during sampling.

Here are several different levels of quantification:

1) Doing enough additional samples to prove that a high-grade deposit justifies bringing in a larger-sized suction dredge to go into production. As part of this, it is important to work out the best type of recovery system to use, and decide how many production-shifts you will run. Night operations require special lighting equipment.

2) Doing enough samples along a stretch of river to prove that high-grade deposits are extensive enough there to justify bringing in multiple production dredges, and setting up a substantial support infrastructure.

3) Doing a series of controlled samples, an equal distance apart, along a portion of a river, to statistically-quantify the value of a mineral deposit. This is often done under the watchful eye of a consulting geologist who will certify the results in preparation for a larger-scale mining operation with the use of mechanized machinery that might float on platforms.

  

 

4) Doing a series of controlled samples, an equal distance apart, for some distance across an entire section of river, to quantify the average-value of the river gravels. This almost certainly would be accomplished under the guidance of a consulting geologist(s) who will certify the results, in preparation of financial instruments for investment bankers or a public trading company.

 

By Dave McCracken

This system combines two classification screens to more-effectively separate material-feed into three separate size-fractions, each which is directed into a different recovery system.

Dave Mack


Riffles in box Three sections of screen

Classification is the Key to Fine Gold Recovery

It is well-established that if you want to effectively recover finer particles of gold, you must first separate them from the larger-sized materials which are being washed through your recovery system by a higher-velocity flow of water. The small-sized material can then be directed to a milder-flow of water over a shorter set of riffles. The smaller you can classify the size of the material, which can be directed by and even milder flow of water over lower-profile riffles, the finer-sized gold that you can effectively recover.

This is all rather easy to accomplish with surface processing plants where earth-moving equipment can be used to feed a plant some distance above the ground. Feeding a plant well above the ground allows plenty of drop for water and gravity to direct material through multiple sizes of classification screens. Then, gravity can be used to direct the different size-factions of material to separate recovery systems with controlled water-flows and riffle sizes specifically designed to recover gold effectively from each size-fraction.

Conventional Suction Dredges do not allow for Much Classification

I am not sure what the exact formula is, but I know from long experience that every inch you lift the feed of a suction dredge above the surface of the water, you lose a considerable amount of suction-power at the dredge nozzle. Therefore, since we have to accomplish both classification and gold recovery from a feed that can only be effectively lifted about 4-to-6 inches above the surface, our options are pretty limited.

Dredge manufacturers have worked out different ways to direct classified materials into slower-moving recovery systems. Generally these methods fall into three categories:

1) Placing a classification screen over top of a set of riffles. This way, smaller-sized material can fall through the screen into a slower-moving flow of water over riffles that are more-protected from higher-velocity water-flow. You see screened-over riffles in common use today.

2) Placing a classification screen towards the head of the sluice box, and then directing the classified material to one or two completely separate sluices which have a slower-moving flow of water over lower-profile riffles. This was most commonly seen in the form of side-by-side triple sluices during the 80’s and early 90’s. While effective, the problem with the side-by-side sluices is that the side sluice(s) normally have to be placed on top of the dredge’s pontoons. Therefore, in order for gravity to make everything work right, the initial feed to the dredge has to be lifted higher out of the water. This causes a power-loss at the nozzle. So you do not see as many side-by-side recovery systems in production on suction dredges these days.

3) Placing a classification screen somewhere towards the upper-end of the recovery system, and directing the classified material to a slower-moving recovery system which is located directly below the main box. This is commonly referred to as an “over-under recovery system, and remains in popular use today. An over-under system is most commonly accomplished in the same basic sluice box, which is constructed with a removable false bottom. By this, I mean two separate recovery systems, one sitting over top of the other, in the same sluice box.

I cannot go into which of these systems are better or worse; because there are too many variables in play, and experienced prospectors can work it out to get the best recovery possible out of any of these designs, each which would likely be comparable to the other. That’s because all three of these system concepts depend upon a single classification screen to remove some portion of the smaller-sized material from the higher-velocity water-flow which is required in a dredge.

This particular discussion has more to do with the effectiveness and size of material-classification. Remember, with conventional suction dredges, we are using water-flow to move all our material across any classification screen(s) that we are using. The larger the dredge, the faster and more powerful the water-flow must be to wash larger-sized rocks and a larger volume of material through the sluice. The faster the flow, the less time that smaller-sized material has to drop through a classification screen. The smaller the openings in the screen, the less opportunity smaller-sized material has to drop through the screen. The shorter the screen, the less opportunity smaller-sized material has to drop through the screen.

Each of these factors combine into to the effectiveness of the dredge’s classification. For example, the substantial flow of water to move 5-inch sized material over 10 inches of 1/8th inch punch plate does not present much opportunity for minus-1/8th material to drop through the screen. So while a separate slower-moving recovery system might be doing a better job recovering smaller-sized gold, perhaps the classification system is only allowing 5% of the finer-sized gold to be directed into the slower-moving recovery system. In other words, the effectiveness of your recovery system is largely affected by how you are attempting to classify and separate the smaller-sized material.

Therefore, on the subject of fine gold recovery with suction dredges, our first challenge is to try and accomplish effective classification as best we can out of a strong flow of water (strong enough to move the largest rocks you are sucking up through the recovery system).

Years ago, we overcame this whole challenge on commercial dredges by working out a mechanized shaker screen at water level which provided 100% classification of the dredge feed. Minus-sized material from the screen was dropped into a sump where it was redirected by a gravel pump to an elevated feed on a surface-type recovery system either on the shore, or on a separate floating platform.

But it is impractical and too expensive to try and place a mechanized classification screen on smaller-sized dredges — which also must remain more portable for sampling. Therefore, on conventional dredges, until someone comes up with something different (if ever), we must continue to make due with a water-flow to wash material across our classification screen(s). With this in mind, here are a few principles which I believe to be true:

1) The faster the flow, the more difficult it is to drop finer-sized material through the openings of a screen in your sluice box.

2) The smaller the holes in the screen, the less finer-sized material you can expect to drop through the openings out of the high-velocity flow required to move larger material through your sluice box. Example: Using the same flow of water and material, you could expect more fine-size material to drop through a 3/8-mesh screen, than a 1/8-mesh screen. This is because the larger openings provide a bigger doorway for material to drop through.

3) The shorter the length of a classification screen, the less fine-sized material you can expect to drop though. Therefore, we want the classification screens to be as long as we can get away with. Longer screen means more opportunity for finder-sized material to drop through.

4) Effective classification of finer-sized material can be accomplished better in stages. For example, first drop 3/8-minus material out of the fastest flow in the box. Then, using a slower flow of water, direct the minus-3/8 material over a 1/8-inch screen.

5) Since we only have 4 or 5 inches of drop to work with from the feed of a conventional suction dredge, there is only room for two levels of classification screen before we must drop the finest-sized material into a recovery system. Otherwise, we will be underwater where reduced gravity is not going to allow water-flow to work for us, anymore.

What to use for a fine-gold recovery system?

material in rifflesAs I have explained elsewhere, I believe it is necessary to direct finer-sized material over lower-profile riffles that will continue to remain fluid under a mild flow of water, even when they are full of concentrated (heavy) material. If you have not reviewed the theory on this, I strongly suggest you read “The Size of Riffles.”

There are different kinds of low-profile fine gold recovery systems on the market. Just take a look around and make your own choice.

We have been using the green, plastic Le Trap sluices to reduce the volume of our dredge and high-banking concentrates all the way back to the early 90’s. I cannot overstate how effective these Le Trap Sluices are. When set up with the proper water-flow, a Le Trap will recover all the visible gold from a feed of minus-1/8th material with losses that are so minimal as to be meaningless. We know this from panning the tailings hundreds of times over the many years.

So when we needed something to recover overwhelming amounts of fine gold using a dredge on a river in Cambodia, I started giving a lot of thought to how we could more-effectively classify dredged material down to minus-1/8th, and direct the material in a controlled flow over Le Trap-type riffles.

Dredge 1Dredge 2

Several very experienced dredge-builders and I created the prototype several years ago from a Precision 6-inch dredge. To accomplish our objective, we assembled two layers of classification screen, each which could be independently raised or lowered, so that we could adjust the water-flow over the riffles, and over each of the screens. The top screen is 3/8-inch mesh. This is to allow the larger-sized material and strong water-flow to wash through the box without affecting the plastic riffles along the bottom. Minus-3/8ths material drops through the top screen onto a 1/8th-inch mesh screen, where the water flow is substantially reduced. Slower water-flow then allows finer-sized material more-extended contact with the 1/8th-inch screen.Double screens over riffles

Material that drops through the 1/8-inch screen is then carried over the Le-Trap sluice by a mild flow of water. By adjusting the height of the lower screen over the plastic riffles, and the slope of the sluice box, we are able to control the amount of water-flow over the lower-profile riffles.

Since the sluice box in the 6-inch Precision was much wider than a normal Le Trap sluice, the prototype required quite a lot of work in a cut and paste project (using of 4 or 5 Le Traps) to create the first underlay recovery system for a dredge.

Fine goldWe invested quite a lot of time and energy into the prototype. All you have to do is look at how much (very fine) gold we found on that river in Cambodia to understand why we did it. We were shipping this 6-incher over to resume (sampling) where we had left off on that earlier project.

 

During trials on the Klamath, I was amazed at how much (very) fine gold we recovered out of just a minute or so of dredging loose material off the surface!

Our trial run on the Klamath River near Happy Camp in March several years ago turned up so much fine gold out of the lose surface gravel, that I hesitated over sending the 6-inch prototype to Cambodia!

I have been told for 30 years that there is so much fine gold in the river that we are losing out of our conventional dredges, if we could just recover it, we could make the river pay just by pumping any gravel! This new system seemed to prove that theory may be true, especially with these higher gold prices. But it was March and the Klamath was cold; so we shipped the original prototype dredge to Cambodia.Cambodia Dredging

I devoted plenty of time in Cambodia (underwater) observing three separate flows of material coming off the back-end of the recovery system; and it was poetry in motion!

I have a non-disclosure agreement with our clients in Cambodia, so I cannot go into details or images of how well the new system performed over there. But I can say that I devoted a lot of time underwater watching water and material exit the sluice box in three separate flows; and the double-screen system is by far the best thing I have seen on a conventional dredge for effectively classifying material into three separate size-fractions.

Because of that, my experienced buddies and I invested quite a lot of time during the 2009 mining season to adapt the double-screen system to my 8-inch dredge. 8-inch dredge

Building double classification screens, so they can be adjusted up and down to allow you to set three separate water-flows through the sluice box, requires quite a lot of labor! But getting this right is the foundation of this whole concept.

Here are some video links which demonstrate the system being used on my 8-incher. These give you a much better look at how we created a double-screen classification system over top of the fine gold recovery: Take a look at the size of the gold we were recovering!

 

As (bad) luck would have it, the State of California imposed a temporary ban on suction dredging just as we completed the double-screen refit on my 8-inch dredge. This forced us up onto the Rogue River in Southern Oregon, where we are limited to smaller-sized dredges. So my 8-incher had to be set aside.

Picking up on the idea of my double-sluice conversion over a plastic sluice, one industry-fabricator was recently promoting the idea of refitting conventional sluices (using the plastic sluice underlay) which do not include the double-screen classification, and do not allow the screens to be adjusted. I would advise caution on short-cutting these concepts. That is what prompted me to write this article. Since these conversions must be accomplished through custom shop work, I wanted to provide you with some background so you can make your own decisions.

While there is still a lot to learn, for the reasons I outlined above in points 1 through 5, I personally do not believe that you can classify raw material effectively from a 4, 5 or 6-inch (or larger) dredge being washed across an 8-mesh screen by high-velocity water.

I believe effective classification must be accomplished in stages; first to drop the 3/8-minus material out of the higher-velocity flow which is needed to push the larger-sized material through the sluice. Then, drop the 1/8-minus out of the much slower flow necessary to wash 3/8-inch material across the lower screen.

I believe you have to be able to adjust the height of each screen (set the water velocity) in order to get a workable water-flow over the riffles and over the 1/8-mesh screen. The water-flow cannot be so much that you boil-out the riffles, and it cannot be so little that you load the riffles. You also must not pack up the space between the two screens!

Eric Bosch and I first experimented with this double-screen concept in the early 90’s. But we made the mistake of fixing both screens (welded them where we estimated they ought to be). Our estimate of how much water-flow was needed between the screens was incorrect; the space between the screens packed solid with material; and the whole system failed.

Also, if you cannot adjust the water-flow over the riffles, and between the screens, you cannot compensate for different conditions in different areas.

Dave's goldAs an example, there is an overwhelming amount of heavy black sand and small iron rocks (and lead) along the Rogue River in Southern Oregon. We do not encounter this magnitude of heavies on our properties along the Klamath River in northern California. The heavies along the Rogue completely overwhelmed my fixed recovery system (buried the riffles on my 5-inch conventional dredge) at the beginning of last season. This prompted me to place smaller riffles below my (fixed) screen, spaced further apart. That worked better, and I recovered a lot of gold. But I believe I lost most of the (very) fine gold (I could see it in the last riffle) that was fed into my sluice box. This has prompted me to refit the recovery system on one of my 5-inch dredges for the upcoming season.

The images at the beginning of this article show an early version of the double-screen system that was designed for deposits we located in Cambodia. We did not find a single particle of gold on that river that was larger than the size of a pinhead. Since larger-sized gold was not present, we did not want to waste the (very) limited amount of room we had to work with by installing riffles for larger gold. Those images are helpful in showing the plastic sluice underlays (there are two of them, one following the other).

The images at the beginning of this article show the Cambodian version of the double-screen refit. Those images are helpful in showing the initial plastic sluice underlays that we were using (there are two of them, one following the other).

Header areaHeader with screen and miners moss

The images in this article also show a header section near the upper-end of the box. My initial theory was that the initial impact of the water and material must bottom-out on something other than plastic sluice underlays. We experimented with a combination of different kinds of heavy screens over top of miners moss or ribbed rubber matting to absorb the initial force of the water and material where it bottoms-out at the head of the sluice box. Fortunately, nearly everything we have tried in the header section seemed to work really well. As you will read below, we have since evolved completely away from using plastic sluice underlays… Header area after running

This is what the header area looked like under the screens when we shut the dredge off while dredging at production speed. You can see how classified material kind of mounds up there before flowing onto the slick plate of the riffle system. We are finding that quite a lot of (very) fine gold also gets trapped in the header section!

We have noticed that while in production, material tends to mound on top of the header section under the 8-mesh screen, and then wash off the mound onto the first sluice underlay. This is really good, as long as the mound does not rise up and pack-up the whole space between the screens.

While we were still using them, the plastic sluice underlays followed just behind the header section. This allowed water-flow and material to settle out and slow down before being washed across the lower profile riffles.

 

 

 

Two kinds of rifflesriffle section

Notice that the shorter section of riffles (remains protected by the top screen) are present only to process classified material which washes across the 8-mesh (lower) screen in the box.

Adding larger riffles for bigger gold

We have since evolved the system, adding two sets of different-sized riffles to catch larger-sized gold. We accomplished this by replacing one of the 1/8-mesh (lower) screens with a solid bottom that supports both sets of the added riffles. The false bottom continues to allow an under current to wash minus 1/8th material across a low-profile underlay, just like in the Cambodia version.

The first set of riffles on top of the false bottom is designed to process the material that drops through the 3/8-inch screen, but is too large to drop through the 1/8th-inch screen (1/8th-to-3/8th size-fraction). This would be for small nugget-sized gold. That size-range of gold is very easy to recover.

As I discussed in The Size of Riffles, the height of a riffle necessary to recover a piece of gold normally does not need to be much taller than the size of the gold you are trying to trap. So the first set of riffles for larger gold can be rather short. Notice that the first set of riffles continues to be protected by an extension of the top screen.

Then we added a final set of open riffles (not covered by a classification screen) to catch any gold we might suck up that is larger than 3/8th-inch (larger nuggets). For example, depending upon where you dredge, the Rogue River in Southern Oregon can produce a lot of gold in these larger sizes. But the river is loaded with fine gold, as well.

It is kind of hard to see in the images; but if you look close, you can see the plastic sluice under the false bottom where we placed the riffles for larger gold.

Since you cannot buy these double-screen systems ready-made, you either have to refit your own sluice, or arrange with a capable fabricator to do it for you. With this in mind, I will follow with some basic directions which we have learned from building several of these systems:

Building the System

If you look at a Le Trap, you will see that it has 3 important sections: There is a slick plate at the top. This is vital; because it allows the water-flow to smooth out before material encounters the riffles. Then there are some short riffles. These capture all the gold unless you over-feed the box with too much material at once, or unless you completely fill the short riffles with gold. Then there are some deeper riffles which more-aggressively capture all the rest of the gold when you do over-feed the short riffles up front. “Overfeeding” has more to do with the amount of heavy iron material, than light sand or gravel. I will talk more about this down below.

Close-up of rifflesThis image shows two sluice underlays following the header section (with no screens on top)

When we planned these sluice underlay riffle-panels, we included the slick plate up front, and then went about 50/50 the rest of the way using short and deep riffles. We did this because I wanted more of the short-type riffles that work so well in the Le Trap. But I did not want to eliminate the deeper riffles which create such a strong back-flow, especially at times when lots of material is being fed across the box. But through extensive trial and error using the third evolution of this system this past season, we discovered that the higher velocity flows that are necessary to move volume-amounts of classified material across the plastic riffles were also causing some of the trapped fine gold to boil out of the system. Too bad! We then tried Keene’s new ribbed rubber matting (good stuff!) and ended up with the same result (we were losing some gold). So it appears that these plastic and rubber riffle systems are better suited for final concentrating work, rather than being used in the volume production setting inside of a dredge recovery system (more on this below).

Because the double-screen assemblies are heavy, in order to manage them, you have to divide your sluice box into several smaller sections. How many sections depends upon how long your sluice box is. You will notice in the images at the top of this article that we divided my 5-inch dredge into three separate sections. One section is over the header area. The other two sections are over top of two identical sluice underlays. It is wise to divide the sluice underlay sections into exactly the same sizes. This way, the parts can be interchanged when it is time to reassemble your recovery system.

We build the double-screen assemblies so they rest exactly upon the sluice underlays. This allows us to take apart one only portion of the sluice box if that is all we want to look at or clean-up.

The screen assemblies are built so the aluminum side supports slide down inside the sluice box and sit directly on top of the side rails of the sluice underlays. This pins everything down snuggly against the bottom of the sluice box. Then we snap the screen assemblies down tight to make sure everything stays in place when we are running the dredge or moving it around on land or in the river.

Sluice Underlays

Close-up of matting
Close-up of both

Through a very substantial amount of trial and error this past season, we discovered that both the plastic sluice material and also the new Keene rubber matting were losing gold from under the twin screens.

Expanded metalWe finally found the right combination by using a wide, raised expanded metal over top of deep ribbed rubber matting. The aggressive expanded metal was dropping the gold out of the classified feed. Once it was in the ribbed mat, the gold was not getting away. This combination was so effective, we even replaced our header section with the same expanded metal, though we used miners moss underneath, rather than ribbed rubber matting.

We did multiple checks; and we were never able to find a single speck of gold in the final 25% of our recovery system, even though we were mostly dredging in fine gold pay-streaks (loaded with fines in the front section of the recovery system) all season.

This is important: The width of the sluice underlays (and screen assemblies) have to be a bit narrower than the inside of your sluice box. Otherwise, it is too difficult to get them in and out when you want to perform a clean-up or reassemble the recovery system. I always allow a margin of around 1/8th or 3/16ths of an inch, maybe even ¼-inch on a wider sluice.

Note: We have since replaced the sluice underlay in the drawing above by welding some 3/4-inch angle iron on both sides of the expanded metal to create side rails that the double-screen assemblies can rest on top of.

The following video sequence should give you a better idea of what we have ended up with as a sluice underlay:

The width of your side rails needs to be greater than the margin you are allowing between the sluice underlay and the side of your sluice box. This is so you will be sure that the sides of the screen assembly are going to slide down and meet the rails of the sluice underlay.

Double-screen Assemblies

Sliding the second screen into the frameThese add up to some weight; so you have to plan how to divide your sluice box into small-enough sections that you can lift the screen assemblies out of your sluice box without too much trouble. On the other hand, you want to minimize how many sections you have to make, because these are very labor-intensive to build.

The length and width of the screen assembly should match the sluice underlay, so that they will marry-up exactly when you set the screen assembly down on top of the underlay.

 

Screen LatchYou have to use aluminum plate for the sides to keep the overall weight of the screen assembly from adding up too much. The height of the sides needs to be at least as tall as your sluice box. I build mine high enough that I have room to adapt a latch to snap everything down tight.

Once you have the aluminum sides of your screen assembly cut to size, bring them all to your local machinist, and ask him to mill slots so that you will be able to raise and lower your two screens. If you bring the machinist one of the lag bolts you are going to use, he can mill the slots just wide enough to allow the lags to slide up and down freely, but not so wide that the lag is allowed to turn in the slot when you are tightening or loosening the nuts that hold the screens in place. Just to make sure I will have the full range of adjustment, I have the slots milled nearly the full height of the sides, to within about ¾ inch of the edge, equally at the top and the bottom. Each aluminum side needs three slots; one on each end and another in the exact middle.

You can source thin-headed lag bolts from fastener supply outlets. If you look, I’ll bet you can find them on line. If you cannot find them, then you have to grind the heads down on regular lag bolts, because normal heads are too thick and will take up too much space between the screens and the sluice box.

Helpful hint: The head-thickness of lag bolts on both sides of the screen assembly need to be included when you are deciding how wide your screen assembly and sluice underlay need to be for everything to slide in and out of your sluice box without too much difficulty.

Another helpful hint: If you cut the side plates all the same size, and have the machinist mill the slots exactly the same on all the plates, all the pieces will be interchangeable, and then you can jig-up to drill standardized holes in the side rails to your classification screens.

The lag bolts need to be heavy enough to support the weight of your screens (perhaps 5/16ths or 3/8ths). Different boxes have different widths, meaning heavier screens. It is better to go a little heavy on the lag bolts. The bolts need to be long enough to extend through the aluminum side, through the side rail of the screen, and have enough room for a flat washer and self-locking nut.

Screen frameStacking screens

Ideally, you build all your screens exactly the same size, so they can be interchanged. We accomplish this by rigging up a jig to cut all the side rails exactly the same; then to weld the frames all the same; and then to drill all the bolt holes the same. We drill the bolt holes in the side rails a little large to allow some margin for error.

Side rails for the screens need to be heavy enough to support the weight of your screens with you standing on top of them. By heavy, I am discussing rail thickness. Because, if you go too wide, you will limit how close you can adjust the distance between the screens. Thicker 1.25-inch-wide strap has worked well on my refits for the screen side rails.

Unless you want to buy whole new sheets of screen (expensive), I suggest you source used screen at your local metal scrap yard. The one we go to in White City, Oregon nearly always has a large supply in all mesh sizes. I gather that commercial screening plants replace their screens pretty often – most of it still in good enough condition to meet our needs.

The top screen (around 3/8th-inch openings) needs to be heavy enough to span the length and width of your screen assemblies without needing additional support, and without bending or sagging when you stand on top of the finished screen.

The lower screen (around 1/8th-inch openings) needs to be heavy enough to span the length and width of your screen assemblies without needing additional support.

Helpful note: I experimented with a finer-mesh lower screen (about 1/10th-inch openings), and had trouble with small particles of rock plugging up all the holes. We call this “blinding.” It’s when the holes in a screen all become plugged-up (or overwhelmed by too much feed), preventing the screen from doing its job. So it would appear that you do not want to use a mesh on the lower screen much smaller than 1/8th-inch.

Cutting screenWe have had good luck cutting the screens to size using a cutoff wheel on a hand-held grinder. If your side rails are made of thick material, you should be able to cut the screen to size and weld it down directly on top of the side rail frame. Grind all the edges nice and smooth, so your hands are not getting cut up once you start working with these screens on your dredge.

Helpful note: If you weld the bottom screen on top of the side rails, and the top screen on the bottom of the side rails, you will be able to loosen or tighten the center bolts in the side plate much more easily. I am talking about the lag bolts which attach the screens to the aluminum side plates. If you end up with your center bolts between the screens, it is much more difficult to get at them!

Another helpful note: You might want to drill your holes just off center through the side rails. This way, you can still get a socket on the nuts after the screen is welded on.

These helpful notes are things I have learned the hard way!

When you assemble the screens, a good starting point would be so that the bottom screen rests maybe just a little more than an inch above the plastic sluice.

Helpful hint: If you make the side rails on your sluice underlay too tall, it will limit how far down you can slide your lower screen.

We have had pretty good results lifting the upper screen about 1.25 inches above the lower screen.

This is important: To add more flexibility, if not already present, we modify the sluice box supports on the dredge so that we can raise and lower the slope of the box. This creates a very helpful mechanism for adjusting flow rates.

Once in the field, you can make adjustments to sluice slope and height of each screen to work out the needed velocity in three separate water-flows: First, the water-flow across the sluice; then the water-flow between the screens; and finally, the water flow across the top screen.

I already discussed above how to replace the lower screen with a false flat bottom which you can place riffles on top of to recover the larger classifications of gold. In my view, it is more effective to do this in the lower section of the sluice box (though, I mounted the riffles for larger gold in the upper-end of the sluice on my 8-inch dredge). I know this viewpoint is not popular with some prospectors, because they do not want to chance losing a bigger piece of gold that is allowed to get so close to the end of the recovery system. My answer to this is that gold is really heavy stuff! If there is some anomaly (like the gold is attached to quartz rock which makes the piece lighter) that would keep it from trapping in a set of riffles in the back-end of the box, it probably will not drop out in the front portion of the box, either.

Other than in a very rare occasion, the vast majority of the gold you will recover is small enough to drop through an 8-mesh screen. Some important part of that gold is so fine as to be difficult to recover using the recovery system on a conventional suction dredge. The journey of fine gold through 20 feet of suction hose, and then up through a diffuser (flare jet) places most of this fine gold right on the bottom of the material as it first flows into the sluice – right where you want it; right where it is most likely to drop through the classification screens out of the higher-velocity flows, which otherwise can wash it through your box like sand. Better, I think, to get the minus-1/8th gold into a safe holding area as the first priority.

If you look closely at the diagram just above, you will see another reason to put the larger riffles towards the rear-end of a double-screen system. See how all or most of the fines are directed through an undercurrent below the larger riffles? This means the larger riffles will not be getting flooded and loaded up with fine-sized material. So, while fine material gets more exposure to low-profile riffles (where it belongs), the deeper riffles remain more open so that larger gold has a place to drop out of the flow.

But that is just my view. You guys can do it any way you decide to!Riffles just after shut-down

The reason you see rocks on top of the double-screens, is because we turned the dredge off while we were pumping at production speed. See how the riffles are working? They are not loading up, and they are not boiling- out. This means the system was working!

I do my classification and sluice flow adjustments when running the dredge at normal operating speed while I am feeding the nozzle at production speed in hard-packed streambed. I arrange for a second person to kill the motor without notice. Then, when I disassemble the system, I can see how the sluice and screens are performing while I am pumping gold and gravel into them at production speed.

Between these explanations, the drawings above, the images and the video segments, you guys (or the fabricator who will help you) should be able to see how these systems come together, and how they work. They provide you with a whole lot more than I started with!

Here follows a video segment we put together at the end of this last season which demonstrates the most recent evolution of this very effective dredge recovery system:

Other Considerations

Trial runPossible need for added floatation: As I mentioned above, these double-screen assemblies are heavy. So if you do a refit of your sluice, you may also consider adding some floatation to your dredge. When I refit the original 6-inch Precision dredge for Cambodia (image above), I also had new, larger aluminum pontoons made up to provide enough floatation so that I could also stand on the dredge while it was running. Nice!

Having enough water-flow to make double-screens work: Every dredge is a bit different. Before refitting your dredge with a double-screen system, you might turn the dredge up and watch the water-flow across your existing recovery system and estimate if you will have enough water volume to provide sufficient velocity to meet the needs of three separate flows.

Overfeeding the system: Every recovery system has its volume-limits! Since I find nearly all of my high-grade gold associated with hard-pack, I design my recovery systems to process average material which makes up normal hard-packed streambed that was put in place during the evolution of a major storm event. Normal streambed consists of rocks which are fitted together, with smaller rocks and pebbles in-between, with gravel, sand and silt filling the smaller spaces. When taking apart normal hard-packed streambeds, the smaller-sized material only comprises a small fraction of the overall volume. Therefore, I have yet to overwhelm one of these double-screen systems while production-dredging in hard-packed material.

On the other hand, if you go out on the river and just start pumping sand or loose, classified gravel (like tailings), a much-higher percentage of the material will penetrate the screens and you will almost certainly overload (blind) the sluice with too much material – and perhaps even pack-up the space between the sluice and the bottom screen. Let me be clear: This double-screen system is not designed to process sand or loose gravel deposits or tailings from some earlier mining activity!

This same concern is true for any type of recovery system used on a suction dredge. So it is important for you to be mindful of the material that you are feeding into your suction nozzle. If it is a layer of sand or loose gravel, you should either slow down; or you can speed up and pump it through as fast as you can; and then go up and make sure your system is no longer packed-up before you start feeding pay-dirt into your dredge.

The fine gold needs to be present: The only good place to test the effectiveness of your recovery system is when you are feeding high-grade into your dredge. The more gold you feed into the recovery system, the better you can see how well it is working.

Effectiveness cannot be discounted just because you see a speck or two of gold down towards the end of your box. The thing to look at is where most of the gold is stopping.

So many times, I have watched others decide their recovery system is not working, only because they are not recovering much gold. You cannot recover much gold if it is not present in the streambed that you are dredging! So I suggest you reserve judgment until you test your system in high-grade.

 

 
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By Dave McCracken

There can be a lot of gold deposited under and around the boulders located within a pay-streak!

Dave Mack

 

It takes an incredible force of water to move boulders in a river. Once they are moving in a flood storm, they can deposit in low-velocity areas, just like gold does. But, since boulders do not have a higher specific gravity, mass for mass, than most of the other streambed materials, they can be washed downstream just about anywhere in the river during a major storm. So you should not only use the presence of boulders to guide you in sampling. You would be much better advised to focus your attention on the boulders that have been deposited along the common path of gold’s travel.

In shallow streambed material, you can sometimes detect where important bedrock changes are located by noting where the boulders have deposited within the waterway. For a boulder, or a group of boulders, to be found in a specific location along the river’s path, there may be a sudden bedrock drop-off, a large crevice, or some other kind of lower-velocity condition in that area which caused the boulder(s) to be deposited there. Everything in the waterway happens for a reason, even if you cannot always see what it is!

If the boulder(s) is located somewhere along the common gold path, that would be a prime spot to do some sampling. In this situation, I suggest that you do not limit your sampling to the area just behind (downstream) of the boulder, though. Go around to the upstream side of it, as well. Look for any bedrock change which may have caused the boulder to stop there. If gold has moved through that area, that same bedrock change could also have caused gold to concentrate there. Finding the bedrock change that stopped the boulder, and following the bedrock change across the waterway, is a great way to locate the common gold path.

You do not always find boulders with every rich pay-streak deposit. But, it is not uncommon to find many boulders keeping company with a good pay-streak. When you do find them, most of them will probably have to be moved out of your way as you work forward through the deposit.

MOVING BOULDERS BY HAND

There can be a lot of gold deposited under and around the boulders located within a pay-streak. To get most of the gold out from under a boulder and into your suction nozzle, usually the boulder has to be moved at least a little bit.

One of the most useful tools that can help a dredger move boulders is a 5-foot (or longer) steel pry bar. If a boulder is too large to be moved to the rear of the dredge hole by hand, it can sometimes be rotated around to one side so that you can dredge out from under part of it. Then, it can be rotated around the other way to access the remaining gold and material beneath. A long pry bar can be a big help to you in moving boulders around in this way.

The key concern while working around boulders is safety! Loose boulders in and around a dredge hole are the gold dredger’s greatest danger, especially when working alone. Boulders resting up in the streambed material are usually more dangerous than those resting on the bedrock. But, those on the bedrock can cause trouble, too, if they are loose and able to roll – particularly, if the bedrock has any slant to it.

As they are uncovered in a dredge hole, loose boulders should be moved and safely secured as a top priority. They should be placed at the rear of the hole, if possible. But, wherever they are placed, they should be positioned so they no longer pose any threat of rolling into the hole and on top of someone working there. You can place smaller rocks and cobbles under the boulders as necessary, to make certain they will not roll or slide.

If you start to uncover a boulder that is resting up in the streambed material, do not forget about it. Until it has been moved and secured safely, a loose boulder should be foremost in your mind. If it is not yet ready to be moved, and you still need to dredge around it to free it up some more, it can be useful to place an arm or a shoulder against the boulder. This way, you can feel if it starts to loosen up in the material. Do not place your arm, head, or shoulder near the underside of the boulder, however. Because, sometimes a boulder will loosen up and crash down very quickly, without much warning. Physical contact with the boulder is helpful when you cannot keep your eyes on it at every moment. The face mask limits your visual perception underwater – especially when you need to watch what is going up the suction nozzle.

The main concern here is to take all necessary precautions to keep yourself from becoming pinned or crushed beneath a boulder in your dredge hole. If a boulder pins any part of your body to the bottom, it may be difficult or impossible for you to get the necessary leverage to move the boulder enough to get out from under it. And, if you are working by yourself …? I know of two dredgers who ended their careers in just this way.

Also beware of fractured bedrock walls that tower over you. They can fall apart and drop in your dredge hole as you remove the streambed material that holds them in place. I got pinned once by a slab of bedrock that broke free of a wall as I dredged away the material that was holding it there. Luckily for me, it landed on my steel-tipped boot, and that I was dredging with another guy on that day!

The second greatest danger to a dredger usually comes from a cobble falling off the side of the dredge hole and hitting the dredger in some way — like on top of the head. This can finish off a dredger just as surely as a boulder. Or, it may cause some serious pain/injury. Fingers and other body parts can get smashed if you are not careful!

Most trouble with cobbles and boulders can be prevented simply by taking your hole apart with safety in mind. The proper method of taking a dredge hole apart has already been fully covered in my Gold Dredger’s Handbook, so I will not repeat it again here. But, as a point of emphasis, the fastest way to take apart a streambed also happens to be the safest way.

Production dredging goes very smoothly and quickly when you have some area of exposed (dredged) bedrock between the non-dredged material in front of you and the cobbles, boulders and tailings behind you. When you start uncovering a boulder in the material, you should immediately begin planning where you are going to move it, once it is ready.

If you run across an occasional boulder that you cannot move by hand, sometimes you can dredge the material (and gold) out from around and under it without having to move it out of the dredge hole. You accomplish this by moving other, smaller rocks out of the hole to make room for the boulder. In this way, if there are not too many boulders, you can keep moving forward on the pay-streak without the few boulders slowing you down very much.

But, if there are a lot of large boulders down along the bedrock, you will likely discover that at least some of them will need to be completely removed from your excavation if you expect to uncover very much bedrock with your suction nozzle. Some boulders will need to be removed to make room for other boulders as you move forward on the pay-streak. If you cannot remove the boulders from your dredge hole by hand, then you will need some mechanical assistance.

DIFFERENT TYPES OF WINCHES

COME-ALONG: A “come-along” is a portable, hand-operated winching device that can be of considerable help to a small-sized digging program. It can be used to move those boulders that are not huge, but which are too large to be moved by hand. Come-alongs range in size. I recommend a larger version of the better quality, rather than the really cheap, imported models. Come-alongs have a great accessibility factor, because you can carry one just about anywhere. Their operation is somewhat slow. But, they will give you that extra edge when you need to move just a few boulders, and you do not own or want to set up a power winch.

GRIP-PULLER: Several companies make a hand-winching device that rides along on a steel cable. There is a handle that you crank back and forth, similar to a come-along. Each time the handle is cranked in each direction, the device moves an inch or two along the cable. These units also come in different sizes. In my opinion, grip-pullers are a substantial step up from a come-along, both in pulling-power and dependability. I have used these units underwater, but find that the water resistance adds substantial work to the cranking action. Still, when you are working alone, having this device in the hole with you allows you to see what the boulder is doing while you are winching it

Where you can buy winching supplies

USING YOUR TRUCK AS A WINCH: If your vehicle can be driven to a nearby position, you can stretch a cable from the vehicle to the boulder. The proper direction of pull can be rigged up by running the cable through snatch blocks (heavy-duty pulleys) which can be anchored to trees, boulders or whatever is available. Then you can use the pulling-power of your truck to help move the boulders out of the way. Four-wheel drive vehicles work better for this, especially when they are carrying a load to increase tire traction. Suggestion: It is better to connect the cable to something on the vehicle’s frame, rather than just the bumper!

When conditions are right for it, using a vehicle to pull smaller boulders can be much faster than using a come-along. One person operates the vehicle, while a diver is in the water, slinging the boulders. Safety becomes a greater concern when more than one person is involved in the pulling and the slinging of rocks. Communication and coordination between the “puller” and the “slinger” are very important to prevent serious accidents. Suggestion: If you turn the truck around and pull in reverse, you can better-see signals from your partner, and sometimes you get better traction, especially on a 4-wheel drive vehicle. Another suggestion: It is better to keep your vehicle a respectable distance from any drop-offs (like into the waterway), just in case the boulder gets momentum in the wrong direction. I know of guy who got pulled over the side of an embankment by a boulder gone wild!

Larger-sized trucks, tractors, bulldozers, and other heavy equipment can sometimes be used to move bigger rocks with even better results.

AUXILIARY TRUCK WINCHES: Auxiliary automotive winches are also able to move small to mid-sized boulders for a dredging operation with excellent results. Some of those little winching units have a wondrous amount of power. A typical 8,000 or 10,000-pound electric winch will move a surprisingly-large boulder!

If you are going to be using an electric winch, you may want to consider installing dual batteries in your vehicle. It also helps to keep the engine running while you are winching, so the batteries can quickly regain their charge between pulls.

When using a truck-mounted auxiliary winch to pull boulders, it is a good idea to block all four wheels. This precaution helps to keep the vehicle from moving, rather than the rock you are trying to pull. The front tires should be blocked especially well. If there is an embankment to worry about, it is also a good idea to run a safety chain or cable from the vehicle to some additional anchor behind, like a tree or another truck. This will protect against losing your vehicle over the embankment if the boulder happens to roll the wrong way. Sometimes this added measure is necessary just to keep the vehicle from sliding during the pull.

Probably the best kind of auxiliary vehicle winch for dredging purposes is one that can be attached mechanically to the “power take-off unit” on your vehicle’s transfer case, if it has one. With this kind of winch, you can use the full power of your truck’s engine to pull rocks. Not only will this provide you with more pulling power, but you will not have to worry about your batteries running down.

There is also a lot of good to be said for the portable electric and hydraulic winches on today’s market. I know of many smaller-scale and commercial dredgers who use them. They are quite powerful! Portable electric winches can be framed up to (1) attach to a vehicle, (2) be taken out to the dredging site, or (3) even be floated on a platform, where there is deeper water. All that is needed is an automotive battery and a means of keeping it charged up. The portable hydraulic winches can be similarly effective. The winch controls can be extended out on a longer cable and even modified to work underwater, which can be very helpful!

LOG SKIDDERS: Most gold-dredging country is also logging country. So there are quite a few log skidders around that can be leased or hired to pull boulders for you. Log skidders are usually equipped with powerful winches. They can really do a job in pulling the larger boulders! Also, you can drive them into some pretty difficult areas. Hopefully, you can work out a deal that will be ideally suited to your operation; a deal perhaps, where you pay by the hour and have the skidder arrive at a certain time each day, or whenever you are in need of it’s services.

PORTABLE POWER WINCHES: Gasoline-powered, mechanical and hydraulic winches are available in all sizes. Generally, the larger they are, the more winching-power that they produce. But, the added size and weight also makes them more difficult to pack into some of the less accessible areas.

If you find a widespread, rich pay-streak with plenty of large boulders that need to be moved, you should set up on your dredging site the most powerful winch that you are able to haul in there. The more pulling-power you have available, the smoother and faster winching will go.

I never recommend that a dredger buy a portable power winch just because he or she will be dredging. It is probably better to wait until you know exactly what your needs are. I have worked many pay-streaks where no winching was needed at all. And, in many of the pay-streaks that did require winching, a number of the boulders were so large that the small, portable store-bought type of winch would not have been adequate for the job.

You can find some pretty heavy-duty used winches for sale at about the same cost as a lighter-weight, new portable unit. I advise waiting to see what you will need before putting your money into a winch.

Having said that, here is something to consider: Mechanical winches seldom have a control mechanism which can allow the operator to stand away from the machine where all the wrestling is going on (and in the line of fire if a cable breaks). While I have used some wonderful mechanical winches, there was never a time that we were pulling a big rock that I was not worried about something going wrong with all those tons of energy happening right next to me. There is a lot to be said about electric or hydraulic units that will allow you to step away from the danger with the controls in your hand.

WINCHING COBBLES IN DEEP MATERIAL OR SHALLOW WATER

As I have stressed in other articles about dredging, the main limiting factor to progress is in how quickly oversized material (rocks that are too large to be sucked up the nozzle) can be moved out of the ongoing excavation. In deeper streambed material, there can be so many cobbles that there is no longer any room directly behind the dredge hole to throw them. You can run into a similar problem in shallow water, where the cobbles must be lifted out of the water (where they become a lot heavier) to get them behind the dredge hole. In these types of situations, it is common to fill cargo nets with your cobbles and winch them out of your dredge hole in bulk. The following video sequence was taken in an operation where we were removing big lots of cobbles from a deep excavation in just this way:

SETTING UP A HOLE FOR WINCHING

Before you start winching boulders, it is a good idea to first make sure that you have located the lower (downstream) end of the pay-streak. You do not want to winch boulders onto any part of the pay-streak that you will be working at a later time. While the winter storms could possibly move some of the cobbles and dredge tailings which were placed on a pay-streak in error, it takes much more than a winter storm to move boulders from where you winch them. Believe me; it is much better to plan ahead, so you only need to move boulders one time!

BUILDING A RAMP

It takes a tremendous amount of winching-power to pull a boulder up and over another boulder from a dredge hole. The direction of pull is all wrong, and the second boulder will act like a barrier. The winching is much easier, smoother, and far less dangerous, if a ramp is built so the boulders will have an inclined runway to be pulled along. Cobbles can be used to make an effective boulder ramp. Therefore, an important part of setting up your dredge hole for winching is to construct a ramp/runway that can be used to easily remove the boulders, without them encountering difficult obstructions.

It can be really tough to pull a boulder out of a hole without a ramp.

Cobbles can be used to make an effective ramp for winching boulders out of a dredge hole.

One approach to setting up your hole is to dredge around a number of boulders as much as possible to free them up for winching. This way, more boulders can be pulled out of the hole once winching is begun. Then you can come back later to clean up the bedrock with your dredge.

To perform winching effectively, you will need plenty of air line attached to your hookah system. This is because it is necessary for the diver to sling each boulder and follow it to its final destination where he will disconnect it. Then, the sling and cable must be pulled back and attached to the next boulder. Since this process requires a lot of movement, depending upon the distance involved, you may need to attach an extension onto your air line to accomplish this smoothly.

FEASIBILITY OF MOVING BOULDERS

A dredging operation that requires a lot of boulders to be winched is going to move slower than if little or no winching is required. A winching operation almost always requires the involvement of at least one other person, sometimes even two or more. Those “extra hands” will usually expect to get something for their active participation in your dredging project. So you will find that when you need to use a winch, you will be moving slower through the pay-streak, and it will usually cost more to run the operation. Therefore, a pay-streak that has lots of boulders usually needs to pay pretty well to make the additional effort worthwhile.

The following video segment will give you a look at an organized winching program where multiple persons were involved:

Sometimes, you may discover an excellent pay-streak, but find that it lies beneath many boulders that have to be moved. Even though there may be plenty of gold under the boulders, after figuring the time and expense involved in winching, you may conclude that the gold recovery, though excellent, is still not sufficient to make the project economically feasible. Big boulders are not easy to move. Moving them takes time and money; more, sometimes, than the gold is worth. So, to avoid getting bogged down in an unworthy project, keep track of your daily expenses and your daily gold recovery. Then you will have some basis for calculating whether it is financially worthwhile to continue dredging in that specific location.

If your winching helpers are not full-timers on your dredging operation, and if the location is not too remote, you might arrange to have them arrive at a certain time each day to help pull boulders. That way, you can spend the morning setting up the hole to winch as many boulders as possible. Then, when your help arrives, the boulders can all be winched out of the hole at one time. After winching is completed for the day, you can let your winch helpers go, while you go back down and clean up the hole with your dredge. This way, you are not paying helpers to stand around with nothing to do while you are dredging. It can make a difference.

SETTING UP A WINCH FOR OPERATION

When you are using a portable power winch to move boulders in a dredging operation, the winch must be set up on a solid and stable foundation. It takes a tremendous amount of force to move a boulder. Sometimes, the boulder will move quickly. Or, sometimes, the sling will slip off the boulder, causing the cable to suddenly go slack. Maybe the boulder will loosen up and roll the wrong way, causing a sudden, heavy stress on the cable. When these things happen, and they do happen, you do not want your winch bouncing around or sliding off the platform. That could be extremely dangerous! The winch must be stable!

The winch also should be anchored to a solid object behind it which will hold its position much more securely than the boulders that are to be moved. A fair-sized tree, or a large boulder, directly behind the winch platform can work well for this purpose.

Also, the cable or chain being used to anchor the winch must be considerably stronger than the winch’s capability to pull. The last thing you need is your anchor chain or cable breaking while you are pulling a large boulder! This could cause the winch, and the winch operator, to be yanked off the platform, resulting in a serious accident. Undamaged, heavy-duty truck tow chains with the adjustable end-hooks are excellent for anchoring a winch. Make sure you get chains that are strong enough.

Your winch should also be anchored to a point which is lower than it is. If the winch is anchored from a low point, when boulders are being pulled, the winch will be held down more solidly onto the platform. If the winch is anchored to a higher point, during pulling the winch can be lifted off its platform. This can also be dangerous.

Sometimes, you will not be able to find a good location for your winch along the streambank. You prefer a location where the winch can be set up to directly face the boulders to be pulled, and which provides a level, solid foundation with a properly-located, fixed object from which to anchor the winch. But if that is not available, you can almost always find an acceptable foundation somewhere between two large objects along the bank. The platform may require a little concrete work to get it right. The winch can be anchored to one of the objects, while the other object can be used to attach a snatch block (heavy-duty pulley). The cable can then be run from the winch, through the snatch block, to the boulders that need to be moved. One advantage to this rigging setup is that if the cable does happen to break under a great strain, it will be less likely to fly directly at the winch and its operators.

Positioning the winch between two anchors on the bank,
because there is no easier way to get a straight pull with the winch.

When you set up a winch, it is usually best to position it so the boulders will be pulled as much as possible in the desired direction. The boulders will also need to be pulled far enough away from the dredge hole that they will not have to be moved again at a later time. Often, you will not be able to set up the winch in a position where you can directly pull the boulders in the desired direction. For example, you may want to pull them downriver, rather than toward the stream bank. This situation is most commonly corrected by using directional-change snatch blocks. A snatch block (pulley) can be anchored at a point from the exact direction that you want to pull boulders. The cable then runs from the winch, through the snatch block, to the boulder. In this way, you can usually move the boulders in any direction that you desire from a stable winching position along the bank.

Setting up the proper direction of pull by anchoring a snatch block directly downstream in the river.

Directional-change blocks for winching should be very heavy-duty. They need to be stronger than the cable being used, or the capability of the winch to pull. The best pulley is one that can be quick-released from the cable. This way, you do not have to feed all the cable through the block to get rigged for winching. Good winching pulleys are generally available at industrial equipment supply stores and at marine equipment shops. Directional-change blocks can be attached to trees or boulders with the use of additional cable, chokers or heavy-duty chain. You will find that a few extra tow chains (long ones) and chokers will come in very handy when setting up a winching operation. Chains which have the end-hooks on them are best, so you can adjust their length to meet your needs.

To minimize damage to the environment, you can place pieces of wood between the cable or chain and the trunk of any tree that you use as an anchor. When you anchor a directional-change block to a tree or boulder, you are almost always better off anchoring to a low point. This will reduce the chances of rolling the boulder over or pulling down a tree.

When you use a cable to anchor a winch or directional-change block to a boulder, set it up so that the pull will not cause the cable to become pinched (between two boulders or between a boulder and the bedrock) or be pulled into the material underneath the boulder. Otherwise, after the winching, you may have trouble retrieving your cable without having to move the anchoring boulder as well.

At times, you may need to set up a directional-change block, to pull boulders in a desired direction, but cannot find a downstream boulder that is large enough to use as an anchor. In this case, you can run an additional cable out from a fixed object further downstream on the opposite side of the waterway, and attach your directional-change block to the cable. Then, by increasing or decreasing the length of the cable, you can position the block right where you want it.

Setting up a directional-change block by extending it out on a cable from the other side of the waterway.

It is not a good idea to winch boulders with rope, even the smaller boulders being pulled by your truck or a come-along. When you use rope for winching, the rope stretches even if it is doubled-back multiple times for extra strength. And, it stretches. And, it stretches. Then, it breaks. Such breaks can be dangerous when working around boulders. Also, it can quickly exhaust your supply of rope. Rope is just not strong enough for the job. Steel cable is best. You might get a deal on good, used steel cable from the scrap metal yards. Call around to find out who has it when you need it. Scrap yards usually sell it at scrap prices, by the pound, even if it is in good condition.

The cable you use on your winch should always be considerably stronger than your winch’s pulling capacity. The last thing anyone wants to see is a bunch of out-of-control steel cable flying wildly back in his direction. Faulty or worn cable should be replaced immediately and never used thereafter for winching.

Winching boulders involves an incredible amount of force. So does hauling logs by cable. Similar cables are used in logging operations to pull trees to the loading area. I have heard stories of logging cables snapping, flying back, and cutting a man in two. You are dealing with a similar amount of force when winching the larger boulders in a dredging operation.

WINCHING SIGNALS

During a winching operation, it will be necessary to have a diver in the water to set the sling on the boulders. The diver will also need to remove the sling from each boulder after it has been moved, and then return the sling and cable back to the dredge hole for use in moving the next boulder. This process will continue until all the boulders for that stage of the dredging operation have been moved.

Unless the diver is slinging boulders and operating the winch (a very slow way to go, unless the controls to the winch are in the water with the diver), another person must operate the winch, truck or other device that will be doing the pulling. Once you have more than one person involved in the operation, communication becomes a critical part of the process.

If the winch is a smaller one, or if a truck is being used to pull boulders, and the pulling position is in sight of the target boulders, the job might be accomplished with only one winch operator. On the other hand, in a normal two-man operation, if the winch operator is unable to maintain constant eye contact on the area where the winching is taking place, perhaps a third person will be needed to help with the communication. Each situation will be different. Since this need for immediate and accurate communication is a safety matter which requires on-site judgment, you will have to decide how many people are needed to winch safely.

Sometimes a truck can be turned around to pull backwards, and the driver can directly see and simultaneously carry out the diver’s signals. The controls on an electric winch will often allow a second person to be positioned well enough to see what is happening where the rocks are being moved.

While a boulder is being moved, the diver can watch its progress and signal the winch operator to stop pulling and/or give slack on the line so the boulder sling can be adjusted, if necessary, to successfully complete the movement as planned. The main point is that the diver must be able to communicate to the winch operator quickly and without error. The greater the pulling-power and/or speed of the winch, the more important it is that these signals be accurately received and acted upon quickly. Imagine that you are using a powerful winch to pull a large rock with a heavy steel cable and solid anchoring objects. If your boulder gets jammed against something else in the dredge hole so that it will not move, and you continue pulling with great force, something is eventually going to give. And, it might not be the boulder! This uncertainty is what you want to avoid.

If you are using a winch that does not automatically feed the cable evenly onto the drum, the operator will sometimes need to manually guide the cable. Otherwise, on hard pulls, if the cable starts crossing itself and is allowed to pinch itself on the drum, it may become damaged and thereafter be dangerous for further winching. For this reason, the winch operator may need to focus some attention on the winch, rather than on the diver. In this type of situation, it is wise to include an additional person to help relay communication. Someone needs to be watching for the diver’s signals at all times.

Gasoline-powered winches make noise. So does a gasoline-powered hookah-air system supplying air to the diver. The diver also usually has a regulator in his mouth. With all of this noise present, and the diver having his mouth full, verbal signals are usually not very dependable – especially, if there is a substantial distance between the diver and the winch operator. For these reasons, I have often found visual signals to be more trustworthy, particularly when there is a person positioned at the winch to relay the diver’s signals to the winch operator.

In shallow water, hand signals can usually work pretty well. You really only need three of them: “PULL” , “STOP” and “GIVE SLACK ON THE CABLE”. I highly suggest you take a look at the standard set of signals that my partners and I use in our own dredging operation. These can be found in a special video segment included with an article I wrote about teamwork. Otherwise, create your own signals so that they can be quickly and clearly understood, and one signal cannot be confused with another. There is also a section on winching and signals in my video, Advanced Gold Dredging & Sampling Techniques.” You might want to check it out to get some ideas.

At times, you may be faced with the need to winch boulders out of a dredge hole located in deeper water. In this case, the diver will be heavily weighted down to stay on the river-bottom. He may also be some distance from the streambank. In this setting, it may be nearly impossible for the diver to surface to give timely signals to the winch operator. The process of getting up to the surface can simply take too long! When this is your situation, and if the water is not moving too fast, you may consider using a buoy, tied to a rope that is anchored near the dredge hole, to relay your signals. I personally have found the best and safest signals to be: (1) buoy underwater means, “PULL” (2) buoy floating at the surface means, “STOP PULLING” and (3) buoy bobbing up and down in the water means, “GIVE SLACK”.

This method of buoy-signals is relatively safe. If the buoy is anchored a short distance from the boulder, in order to pull the buoy underwater and hold it there, the diver would have to be away from the boulder on the “PULL” signal. If the buoy is floating, the diver can be anywhere, which is why it is the best choice for the “STOP” signal. You need to make certain, however, that nothing is allowed to snag the buoy’s rope (like the pull cable or an air line) which could pull the buoy underwater and cause a false “PULL” signal!

One other safety note:All divers must always watch their own hookah air lines during winching, to make sure an air line (or the signal rope to the buoy) is not snagged up in the cable or rolled over by the boulder as it is moved.

BOULDER SLINGS

When slinging boulders, try to make sure the pull cable will not rub too heavily or get crushed against other boulders. It is always best to protect the pull cable and let the boulder sling take the pounding. The boulder sling is going to be pounded anyway. Because of this rough duty, boulder slings should be replaced or repaired periodically.

One type of boulder sling often used out in the field is a long, heavy-duty tow chain with end-hooks which allow the chain to be quickly and easily adjusted to any length. This system gives you a fast set up. Just wrap the chain around the boulder in the proper place, connect the end-hook to give you the right fit, and she’s ready to go.

Tow chain boulder sling with end hook.

However, some boulders are smoother and rounder, which makes it more difficult to get a good “bite” with a sling made out of chain. Every time you start to pull, the boulder might move just a little and then the chain slips off. You can waste a lot of time working on a single boulder in this way; it can get quite frustrating.

Logging cable-chokers are also useful for making a cable sling that will tighten up on the boulder as you pull. This may improve the situation, but still not work problem-free on smooth, round rocks.

For round and smooth boulders, I have found the best remedy to be an auxiliary “boulder harness.” This homemade boulder harness consists of heavy cable, chain, steel pipe and cable clamps. It is very easy to construct. The sections of steel pipe slide onto the cable to protect it and to keep the cross-chains properly positioned. The harness is set up like a lasso. It pulls tighter around the boulder as stress increases on the line. And, it generally works well in pulling even the most difficult boulders.

How to put together an excellent boulder harness for winching.

PULLING BOULDERS

Some boulders come easy and some do not. A lot of the problem is in breaking the boulder’s initial suction/compaction in the streambed. If your winch does not have the power to pull a boulder the way you have slung it, sometimes you can break the boulder free by using a rolling hitch A “rolling hitch” is rigged by slinging the boulder backwards, then running the chain or cable over top of the boulder. This places the winch’s pulling-power along the most-leveraged position on the boulder. This will sometimes free a stubborn boulder by rolling it.

How to sling a rolling hitch.

When pulling boulders up and out of a dredge hole, you should pull them some distance away from the hole. Otherwise, if there are more boulders to be moved, they may begin backing up along your ramp and block the passage of any more boulders. This could require you to move them all again, which is a time-waster that you can avoid with proper planning in the first place. For example, take a look at the image at the beginning of this article. That is a top view of a winching operation we did on one of our Group Mining Projects a short while ago. See how we were pulling the boulders back well out of our ongoing excavation?

If you are dealing with relatively deep streambed material and a lot of boulders, you may want to set up an adjustable, directional-change block behind the hole. This way, the boulders can be winched out of the hole in several different directions. This will prevent them from backing up so quickly.

Setting up an adjustable directional-change block to pull boulders in several different directions.

Once the dredge hole has been opened enough, some of the boulders can be winched or rolled to the backside of the hole, rather than taking them up the ramp. Winching will start to go faster when you get to this stage. Depending upon the situation, it may be necessary to winch some of the boulders up the ramp and out of the hole to prevent too much jamming. Be sure to keep access to the ramp free and clear. Otherwise, you may get closed in with too many boulders in the rear of your hole. The more boulders that are jammed up, the more difficult it can be to clear them out of the hole.

Sometimes, when you have winched your boulder to its destination, it will end up on top and pin your sling underneath. If you are using a tow chain as your sling, you can usually just unhook it and have the winch pull it out from underneath the boulder. But, if you are using a sling made of cable, you may not be able to pull it out from under the rock without damaging the harness. For this reason, it is a good idea to have a second sling on hand to help move the boulder off the other harness when this happens.

DIVER’S SAFETY

A diver will be safest by staying well away from the area where a boulder is being winched, and the path it will be taking as it is being pulled. The forces involved in winching are more than enough to cause a very serious accident. Since the diver is underwater, the winch operator sometimes cannot see what is happening where the bolder is located.

What can happen down there, though, is when the diver sees the boulder getting hung up on things as it is being pulled along, he wants to move in and help it along with his pry bar. The less power that your winch provides, the more the diver will naturally feel the need to help the boulder along in this way. Never forget that your safety margin is considerably reduced when you get near a boulder while it is being pulled! A safer course of action would be to stop the pulling and reset the harness, or reset the direction of pull, or improve the boulder ramp, or find a stronger winch for the job. Or, you can increase the pulling power of your existing winch by double blocking…

DOUBLE BLOCKING

“Double blocking” is accomplished by attaching a snatch block to the boulder sling, running the pull cable through that block, and then back to the last directional-change anchor. This type of rigging will nearly double the amount of pulling force that can be exerted against the boulder by the winch and pull cable.

Double blocking back to the last directional-change anchor
will nearly double the winch’s pulling power against the boulder.

If even more power is needed, another block can be set up on the line to run the pull cable back to the boulder sling. The pulling force of any winching device can be increased by continuing to double block in this way. There is a disadvantage to all this rigging, however. It takes much more cable to pull boulders any significant distance. Also, it is equally more difficult for the diver to pull the boulder sling and cable back to the dredge hole after each boulder has been moved. With all that cable going back and forth, it can get pretty complicated – especially if you are dealing with a limited amount of visibility. Quick-release snatch blocks are a must when double blocking. This way, you can detach the pulleys from the cable without having to feed it all the way through.

Actually, one double block is not that hard to manage as long as you have enough cable. It is when you double block a second time that it starts getting difficult to keep track of which cable is going to where? But, this alternative is available to you if you need the extra pulling power to move a particularly large boulder.

Directional-change blocks, by themselves, do not give you an increase in pulling power. For a power increase, the cable must be doubled back so that the boulder is moved only half the distance that the winch is pulling on the cable.

 

 

By Dave McCracken

As far as I’m concerned, if you are going to spend a lot of time dredging in cold water, a hot water system is definitely the way to go!

Dave Mack

Cold Water 1
“Photo by Tim Cook”

Can you recall ever standing alongside an unheated swimming pool or just next to the water’s edge on the beach, trying intently to muster the nerve to jump into the cold water? Perhaps you even tried to build up to the big leap by counting, “One, two, three.. .jump!” — only to find yourself still standing at the edge of the water after the countdown and feeling like your body is not quite under your control. This can often be the case when you are dredging in cold water. The key to successful cold water dredging is having the proper equipment — particularly those items needed to keep your body from getting too cold and uncomfortable.

Wetsuits

Wet-suits are designed to allow water to get inside the suit. Your body-heat then warms the water up, insulating you from the colder water that remains outside the suit. In really cold water, the main problem with a wet-suit is that initial frigid shock which shocks your body as the initial cold water rushes into your suit when you first enter the water. This happens again every time you re-enter the water after knocking out a plug-up in the jet tube or every time you take a break. This “cold water shock” has an accumulative affect on the body; and even the toughest people often find ourselves going “one, two, three” on the bank and have trouble making our bodies jump back into the water.

Some wet-suit divers lessen the pain of cold water shock by having a hot tub of water on the bank. They pour the hot water into their suits just before re-entering the water to help bring up their body temperature. Hot water systems that provide a steady flow of warm water into a wet-suit are even better — but we will address that topic below.

There are different types of wet-suits, some which are designed especially for cold water use. Cold water wet-suits are usually made of thicker rubber, have few or no zippers, and almost always have the hood directly attached to the wet-suit top. There is also the “shortie,” which is like a pullover wet-suit sleeveless T-shirt with or without a hood attached. A shortie can be worn underneath or over top of a regular wet-suit to create added warmth. In addition to the added thickness of rubber around your upper torso, a hooded-shortie prevents a lot of the cold water shock from running down your neck and back!

Important note: The more rubber you add for insulation from cold water, the more lead you must add to your weight belt(s) so you can remain firmly anchored to the bottom of the waterway when you are dredging. Also: The more rubber that is added around your upper body, arms and shoulders, the more constrained your arms and shoulders will be. Dredge work underwater is mostly stomach, arms and shoulder-work (movement). Therefore, adding more rubber increases the amount of effort required to get the work done. Effort in dredging is like money in your wallet. You only have so much. So it must be managed as efficiently as possible. Because, once you have used it up, your day is over.

Dry-suits

For cold water dredging or diving, dry-suits are definitely a step above wet-suits (when there is not a hot-water system). A dry-suit is designed to keep all of the cold water out. Basically, there are two different types of dry-suits available on the market: Those that use the rubber or nylon shell as insulation, and those that require additional insulation to be worn inside the suit. Both types work well; it is a matter of individual preference as to which kind is best for you.

Dredging activity is very hard on any type of suit. There are many different models and makes of dry-suits available. Some are designed more for sport diving rather than dredging and hard work. Dry-suits generally are quite a bit more expensive than wet-suits. However, you cannot rightfully put a price on comfort and warmth when you are spending many hours underwater working for a living. If you are cold and uncomfortable, you will not get in as much dredging time; and you will not make as much gold (money). So, my advice is to spend the extra money on getting a quality dry-suit if you are going to buy one.

Dry-suits generally require more maintenance than wet-suits. Mainly, the seals at the extremities and the zipper must be properly maintained. Most dry-suits have zippers which should be coated with bees wax every several uses and sprayed with silicone each time the suit is used. The seals should be sprayed just before each use. This allows them to slip on more easily, and prevents unnecessary stretching. The zipper is the heart of a dry-suit and must be handled with care. You have to be careful not to get sand in it, and not to sit on it or rub it heavily while moving rocks around in the dredge hole. I always glue a rubber flap over my dry-suit zippers to further-protect them from dredging wear and tear. Most manufacturers stress having a second person zip it closed rather than doing it yourself. This is because it is difficult to pull the zipper straight when it is behind you, as many dry-suit zippers are. If you damage the zipper, the suit is no good until you get the zipper replaced.

You will find that even the smallest puncture holes in a dry-suit need to be patched when diving or dredging in extremely cold water. Otherwise, you are constantly uncomfortable with cold water entering the suit from that location.

Hot Water Systems

Cold Water 2As far as I’m concerned, if you are going to dredge long hours in cold water, a hot water system is definitely the way to go! Water is usually heated with a heat-exchanging device mounted to the cooling or exhaust system of the dredge motor. The dredge pump is tapped to provide a water supply, which runs through the heat-exchanger, then through a steam trap/mixing tank, and then down through a hose to pour a constant volume of warm water into the dredger’s wet-suit. Some dredgers are using propane continuous-demand hot water heaters, but most use heat exchangers mounted to their engine exhaust systems.

Hot water heat-exchangers are available on the market. They are also reasonably easy to build. Most homemade exchangers are built with a long length of copper tubing which is either wrapped around the existing exhaust system or is coiled inside a separate housing through which the engine’s exhaust is channeled.

Photo By Tim Cook

The key to a hot water system is to provide an abundance of hot water. If you do not have plenty of hot water for all of the divers working on a system, then you will most likely end up pumping cooler water into each diver’s suit, which can be worse than having a wetsuit with no hot water system.

Hint: You can never have too much hot water — because you do not necessarily have to use it all.

Most ordinary wet-suits are adequate as hot water suits — particularly with the addition of a hooded shortie vest. Dry-suits normally do not make good hot water suits, unless they are modified. This is because the seals prevent the hot water from exiting the suit. After a while, all the excess water inside the suit cools down and makes the diver cold. Removal of the seals on a dry-suit would probably make it a good hot water system (as long as it is a tight-fitting dry-suit) — but this seems a waste of money when a far less expensive wet-suit will accomplish the same purpose.

The main problem dredgers can have with a hot water system is being scalded by extreme hot water or steam. This problem can largely be solved by adding a steam trap to the system. Some prefer to call this a “mixing tank.” A mixing container can be made out of PVC plastic tubing. One of the primary purposes of the mixing container is to be a holding tank for water and steam. So, if extreme hot water or steam is created in the system, it will have a chance to mix with the warm water in the tank before being pumped down to the diver. The mixing container should be mounted vertically on your dredge with the input coming from the top, and the output to the diver being on the bottom of the container. This way, steam is prevented from being pumped directly to the diver(s). Some systems contain a low-pressure relief valve at the top of the container to allow air and steam to release.

mixing containerThe mixing container must be large enough to absorb a shot of extremely hot water, but not so large that it allows the water to cool down before it is pumped to the diver. The mixing container allows the diver to feel the rise in water temperature much more slowly, so that the hot water hose can be removed from the wetsuit before it gets uncomfortably hot. Sometimes, the water can be so hot coming out of a heat exchanger, that a special steam hose must be used. In fact, just for safety, I always use heat hose on the connection from the heat exchanger to the mixing tank.

If the water coming out of the heat exchanger is too hot to pump directly to a diver — which is often the case — a source of cold water can also be tapped from the pump and directed into the mixing tank through a valve. By regulating the amount of cold water, you can adjust the temperature of the water being pumped down to the diver. This also increases the volume of warm water available to all of the divers.

Warm water is usually pumped down to the diver through the same kind of hose being used for air line. The hot water line and air line are usually taped together to prevent tangling and additional underwater confusion. The hot water line can be slipped into your wet-suit down through the neck. I usually poke a hole in my wet-suit near my chest where it is easy to slip the hot water line in and out of my suit.

Or, in extremely cold water, you can devise a splitter system which will direct some of the warm water to your chest, hood, each bootie, and each glove. This is the best way to do it if you are dredging in ice cold water. However, sometimes the splitter system can be avoided simply by having a hot water system which provides so much volume, that the warm water is forced out into these same extremities.

When dredging in ice cold water, if you do not have warm water directed to your hands, it is usually necessary to use three-finger wet-suit mittens. Otherwise, your hands can go numb from the cold. Three finger mittens are bulky; they prevent you from picking up larger cobbles with one hand, and they generally slow you down. With a good source of hot water to the hands, you can often get by with a good set of slightly-insulated rubber work gloves with the openings loosely rubber-banded around your wrists to prevent cold water from entering.

Dredge with snow on the decksAuthor was developing some of the early hot-water heaters on his first dredge in 1981 while working in the frigid waters of the Trinity River in Northern California.

It is necessary to warm up your dredge engine to normal operating speed for at least several minutes to properly set the temperature of the water directed to the divers from the mixing container. Once you get the temperature working right for you, you normally do not need to make any further adjustments on subsequent dives, as long as you are running the motor at the same RPM.

If you stand around for a few minutes with hot water pouring into your suit, there is usually no shock at all when entering the cold water. As a matter of fact, it can be a pleasure to enter the cold water after you run your body temperature up to the uncomfortable stage when you begin sweating.

A hot water system should be removed from the dredge when not being used, like during the warm summer months. Otherwise, the heat and vibration will tend to wear the heat-exchanger out unnecessarily. Also, even when not in use, if a hot water system is attached, water should be allowed to flow through it any time the engine is running. This will prevent unnecessary overheating of the heat-exchanger.cold water 3

Photo by Tim Cook

If you are tapping your dredge pump for a supply of water, be sure the water output is either closed off or underwater when priming your pump. Otherwise, there may be an air leak which can prevent priming.

The nice thing about a hot water system is that it will supply a continuous feed of hot water into your suit. This way, your body’s energy reserves are not being constantly used up to keep warm. As a result, you can be comfortable and get in more dredging time.

Important note: You can also be so warm that your body doesn’t want to work — like being in a hot shower. The solution to this lies in the amount of cold water you valve into the mixing tank, or how far down you zip your wet-suit jacket! Believe me, “too warm” is a much easier problem to solve underwater than “too cold.”

A common question people ask is, “Should I get a hot water system, or a dry-suit?” The answer to this lies in what you intend to do. I suggest having both systems available, depending upon your activity. For production dredging and sampling in extremely cold water, I would use a hot water system. For swimming across the river to stretch a rope, or for swimming down the river with mask and snorkel to look at the bottom in extremely cold water, I would recommend a dry-suit.

Other Things To Know About Cold Weather Dredging

If you are working in freezing temperatures above water, there are certain things that should be done on your dredge each day before knocking off. Your pump should have a drain plug tapped into the bottom. This way, you can drain the water at the end of each day to prevent your pump from freezing solid. It is not a bad idea to bring some hot water with you everyday in a thermos, because sometimes the pump will freeze even with the water drained. Be careful not to crack the pump housing by pouring too much scalding water directly over it when it is freezing cold.

Also, in freezing weather, the concentrates and water must be completely cleaned out of your recovery system at the end of each day. Otherwise, they will freeze solid and prevent the system from working until it thaws out the following day — if it thaws!

If you are not going to process them directly, your concentrates from the day should be stored well underwater to prevent them from freezing on the bank. Your mask, hood and gloves should be brought back to camp each evening and kept warm. Otherwise, you have the misery of putting them on when they are ice cold — unless you have a hot water system on your dredge.

Winter Dredging

Eric Bosch and author displaying nuggets pulled while diving together.

Dave and Eric holding nuggetsEven if you are able to handle most of the cold water problems with the use of good equipment, another factor winter dredgers often have to deal with is higher and faster water. While the higher water will allow you to mine further up on the edges of the river, in many areas it will prevent you from mining out in the faster and deeper water areas-which may provide easy mining during the summer months. If, due to the faster, higher water, you are not able to get out and sample in certain sections of the river, you will not be able to run a full testing program on that section of river; and you will miss pay-streaks. So, it can also be more difficult to locate deposits during the faster and higher water months of the year.

On the other hand, if the river edges are paying, the winter months may be the only time they are available for dredging. The location of deposits are going to vary from one place to the next.

While wet-suits, hot water suits and dry-suits do make for good insulation underwater, they generally provide poor insulation to the cold air above water when you are wet. Therefore, it is good to have a warm winter jacket to wear over your diving suit while taking breaks on the surface.

Tents in the snowAs a side note on this, my commercial dredging buddies and I ate many hurried lunches on deck during the winter months (even while it was snowing) while the dredge continued to run at operating speed (with a rock placed over the suction nozzle to slow the water in our recovery system), pumping warm water into our suits.

If you are mining in extremely cold conditions, it really helps to have a warm and comfortable camp. A person can put up with some pretty cold and miserable conditions if he or she knows there is a warm shower and hot meal coming later that evening. There are few things worse than freezing all day and then going back to stay in a wet and cold camp!

Author’s campsite during his first several years as a gold prospector.

How Tough Are You?

It takes a pretty tough person to dredge in extremely cold conditions. Even with the best equipment, there is still a substantial amount of cold water exposure on your hands and face. You spend quite a bit of time working on the dredge, tying off lines, swimming the river, cleaning up concentrates, making repairs, etc. This all adds up to exposure which can be painful or uncomfortable. Some people are gung-ho enough to dredge in extremely cold water on a short-term basis. Few people are willing to do it long-term.

We all have the potential to be tough enough to dredge in extremely cold water. What it always comes down to is whether or not we desire to be that tough! A lot of people think they are, and then realize they are not willing to do it!

Talk is cheap!

I was mining with several guys in 34-degree water one winter. One of the divers and I were sampling for a new deposit while the other two guys were actively dredging out a rich deposit we had already located. They were recovering several ounces of nugget-gold each day, while we were knocking out sample holes. One day, we helped get the production operation started and then headed out to do our sampling. We soon realized we forgot our lunch, turned around and drove back to where our partners were dredging. We had not been gone fifteen minutes, and they had already gotten out of the water and were in the truck with the heat turned on — drinking hot coffee! These were tough guys; that water was cold!

A partner and I were dredging in Alaska in October when things started to freeze. We’d had a very good season, but I wanted to put more ounces into my bottle before returning home. Ice had already formed on the edges of the river, and my partner had been ready to leave weeks before. I was determined to spend one more week dredging, because the gold was good and I had plans for what I was going to do with it. One day, with a week to go, I could not make my body go underwater again. “One, two, three, go!” — but my body refused. So, it just wasn’t worth it, anymore! I walked over and tugged on my partner’s air line and asked him if he was ready to go — home, that is. We were on the road later that afternoon in a warm truck with the heat blasting. In that area of Alaska, three feet of snow fell that night!

There is a point where the body just takes over and says, “No!” And, this is probably the point where it is smart for you to listen.

 

By Richard Doherty

“With the new instruments available today, millions of gold nuggets are within reach of the intelligent, properly equipped, electronic prospector.”

 

Hand full of beautiful gold nuggetsWhen I first heard about picking gold nuggets from the surface, or close to the surface of the ground, I really didn’t think it was feasible.

I made some halfhearted attempts at locating some of the precious yellow beauties with no success and much frustration. Finally, I buried a gold nugget down in the ground and attempted to locate it with my new detector. To my surprise, it wouldn’t detect the nugget, so I moved it closer to the surface and still couldn’t detect the target. It was almost on the surface by the time I was able to receive a very light audible signal. That did it! I quit!

Still, the idea of locating a gold nugget with an instrument really intrigued me, so I stayed in touch with the advances of metal detectors. In the meantime, I continued my more conventional prospecting activities in Arizona, where I was fortunate enough to associate with other prospectors who knew about gold deposition.

Years later, the metal detector industry began to develop detectors that would deal, at least somewhat, with the highly-mineralized ground associated with gold deposits. So I purchased one of the most advanced detectors on the market and went in hot pursuit of the elusive yellow nuggets. Hour after hour, I combed the ground; I searched everywhere the gold “had to be!” If it was there, I wasn’t finding it, so I pressed on.

Scorpion made from gold nuggetsFinally, after many, many frustrating hours, the first nugget succumbed to my detector, minutes later, another. I really got excited, and I decided to share this new-found activity with my friends. I helped them learn what I had learned, and then we developed new methods and techniques. Detectors were getting better, and I purchased the latest equipment, knowing that I needed every edge that I could possibly acquire.

We sorted out which instruments worked best and figured out how to get the most from the ones we decided to work with. Nuggets began to fall on a regular basis, and more friends became interested. We turned them on to the equipment we were using and the techniques we had developed. They began to find gold nuggets almost immediately. This surprised me; because after all the heartache I went through to locate my first nugget, my friends were quick to pick up what we had already learned.

Gold nugget hunting is not like coin hunting at all; it is a specialized field and requires specialized equipment and techniques. Once learned, it is easy. As you do it more and more, nuggets will yield to your detector more consistently.

First, there are three “musts” for any degree of success. Not one of them is any more or any less important than the others, because they are dependent upon each other:

1. The correct instruments must be selected. Selection is based upon the instrument’s performance relative to the size and purity of the gold and type of ground that will be searched.

2. Knowledge regarding the use of your instrument must be thorough.

3. Knowledge about where the gold is located. Most of this information is gathered through research and talking with others who already know.

Your degree of success depends upon how diligently each one of these three “musts” is followed, and it is that simple. If you decide to approach finding gold nuggets in this manner, it is not a matter of, “Will I find a gold nugget?” It is only a matter of when, how big, and how many!

Huge rough nuggetIt has never before been more possible to locate your own gold nuggets with the aid of a metal detector, than it is right now. It is not that there is more gold out there. In fact, each day, there is a little less. However, with the new instruments available today, millions upon millions of beautiful gold nuggets are now within easy reach of the intelligent, properly-equipped electronic prospector. You don’t need tons of equipment to haul around, nor do you need many thousands of dollars to get started. The exercise is mild; the air is fresh; and the pursuit of your own gold nuggets is done at your pace — no one else’s.

I would also like to mention some of the myths surrounding electronic prospecting. It is difficult to place these in any order, so I will just mention them according to the frequency of times I am asked:

“Are there still gold nuggets out there to be found?”

“Will a metal detector really find gold?”

“Didn’t the ‘old-timers’ get all the gold?”

“Why isn’t everybody doing it?”

“Isn’t all the land claimed up?”

“Don’t I need a specialized vehicle or mode of transportation to get to the gold?”

“Isn’t it hard work?”

“How can I find gold nuggets when I know nothing about geology, mining, mineralog, or electronics?”

“Won’t a detector find fool’s gold?”

Please don’t let these questions, objections or myths stop you from gathering your own gold. It’s a whole new exciting, profitable activity, and you can do it!

Public awareness is definitely on the increase, and hundreds are getting into the activity of capturing gold nuggets from the earth. There are pounds of gold being taken daily, and there is no reason why you cannot be taking your share!

Frustration and lack of confidence is the primary cause of failure. The reason most electronic prospectors fail is that they purchase inadequate equipment or don’t learn how to use it properly.

Hunting coins and hunting nuggets with a detector are quite different. Coins are a flat-sided target. Many nuggets are not. Also, many flat nuggets will slip sideways into a crack or crevice in the bedrock, which leaves very little target-area available from the surface. Shape, size, and lack of the “halo” effect can cause a gold nugget to remain a difficult target.

Of course, there are exceptions to this. Not too long ago, I found a 5/8-ounce gold nugget that was about one inch deep, lying flat. It sounded-off like a quarter! I was amazed to retrieve a beautiful nugget which was shaped like an eagle’s head!

Nugget hunters know how important good equipment is. I was speaking with a professional electronic prospector the other day, showing him a new detector. Before I could tell him what the detector cost, he said it didn’t matter anyway; because he was willing to spend any amount of money on the detector if it was significantly better than the one he was using. You see, he knows that good equipment will pay for itself, especially with the price of gold nuggets as they are.

I know coin hunters who dream of finding their first gold coin. Most never do. However, electronic prospectors, who follow the basic guidelines, will find hundreds of gold nuggets.

Where is the gold? This brings us to another reason why now is an excellent time to get started in this fascinating activity. There are clubs and various types of associations which you can join where you will meet other people who prospect. Some of these organizations provide mining properties for their members to prospect. The folks who run clubs are usually quite particular about the mining properties which they own, and they are also knowledgeable about which claims they should stake or purchase. One of the easiest and fastest ways to find gold is to join one of these clubs. Some even provide training programs or organize group mining projects where you can gain immediate, valuable hands-on experience. Talk with other members and the staff to gain information as to where you might begin your prospecting. This is the best way I know of to get started in any type of gold prospecting today.

As you prospect on these claims and talk with others, you will begin to get a “feel” for where the gold is and why it is there. Gold seems to be a lot easier to find if you already know it is there. If you are not sure, it could cause you to search halfheartedly, and that is not conducive for locating nuggets. You must know the gold is there; you must know how to operate your equipment; and you must know that your equipment will get the job done. If you have these three criteria well in hand, you will surely find your own gold. After that, it’s just a matter of spending some time doing it and improving your skills.

In the beginning, it may take you a minute or longer to recover a target you have established; but soon, these targets will be coming out of the ground so quickly that you will surprise yourself. My average recovery time per target is between fifteen and thirty seconds, depending upon digging conditions. I have seen it take as long as 30 minutes to extract a target, but these are more unusual conditions.

In Quartzsite (Arizona) last year, we had occasion to dig in some very old material that was as hard as concrete. This material had been deposited millions of years ago. There was no man-made metal present. But the gold was there! My detector sounded off, and we knew what it was; so we started to excavate. It was hammer and chisel time! You must be very careful not to scar the nugget, so digging has to be carefully-done. Almost 30 minutes later, out came a beauty. It weighed just over ½-ounce. It was detected under 13-inches of highly-mineralized, concreted earth and rock.

As you uncover a valid target, it will usually develop into a clearer signal or stay about the same. If it stays the same, you may also have passed over an area that is highly mineralized. Or perhaps there was some kind of hot fire in that spot during some time in the past. Sometimes, ashes will read very slightly on the detector. But the signal does not develop as you dig down on it.

If the signal disappears altogether, you have either moved the target, or you may have had a piece of rusting ferrous material that fell apart when you moved the soil. A magnet comes in handy to quickly isolate ferrous targets; it can be a real time saver!

Bullets, nails and other foreign metallic targets are some of the items you will learn to deal with. At first, they are nothing but a nuisance. However, let’s take a closer look at this: If you are digging metal of this nature, not only does it hone your recovery skills, but it tells you that the area has not already been searched-out (every smart, responsible detectorist has a container along to remove small metal trash-targets from the playing field).

If there are no previous dig-holes, you may be the first person to detect that area. But if there are dig-holes, and you are still finding metal, it tells you someone else did not do a thorough job. If they left trashy metal in the area because they were using an electronic discrimination mode, they certainly will have left nuggets behind, too! You will pick up the nuggets your predecessor left, because electronic discrimination seldom can be used effectively while nugget hunting. Only under certain conditions would you use discrimination, and that would be after many hours of experience. Even then, you could make costly mistakes. My advice is to not use electronic discrimination while hunting gold nuggets.

Meters, gauges, bells and whistles do not make a good nugget-hunting detector. I personally feel about the only function they serve to the nugget hunter is to add weight to the instrument — which is the last thing you need. Although I will admit that there are other good prospectors around who disagree with my opinion.

The following is a list of recommended reading material which may call for reading and re-reading. This is not a complete list, but the material suggested here is a must:

Willie Merrill wrote a book called, THOSE ELUSIVE NUGGETS; and he not only knows what he is talking about, he shares his knowledge in a very free manner. I have read the book no less than five times. Each time, I learn something new. Our minds are not always ready to accept all information the first or second time through.

Another book of importance is ELECTRONIC PROSPECTING by Roy Lagal and Charles Garrett, which will also require more than one reading. This book goes into the many avenues of electronic prospecting.

Any magazine articles written by successful electronic prospectors are definitely worth reading. Hundreds of articles could be written on the subject of electronic prospecting, and each one of them will have some hot tips for you. .

 
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This story first appeared in Gold & Treasure Hunter Magazine May/Jun, 1993 on Page 45. This issue is still available! Click here.

By Dave McCracken

Classification is necessary to increase the amount of smaller particles of gold that you will trap in your recovery system.

Dave Mack

 

It takes more water velocity to move larger-sized material than it does to move the smaller-sized material through a sluice box. Yet, to the degree that the water velocity over a sluice box is increased, there may be a loss of fine gold recovery. Or, to the degree the water velocity over a sluice box is slowed down, there is likely to be an increase in fine gold recovery–as long as there is still enough flow over the box to keep the riffles concentrating.

When larger rocks are pushed through a sluice box by water force, they also create greater turbulence behind the riffles as they pass over, which may cause an additional loss of fine gold.

To improve gold recovery, it is common practice to run material through a screen to classify out the larger rocks before running the material through the recovery-portion of a sluice box. In this way, less water velocity is needed through the box, which allows for a more orderly flow, and an increase in fine gold recovery. The action of screening materials is called “classification.” Materials which have been passed through a classification screen are called “classified materials.” The following video segment demonstrates this very important point:

The size and depth of riffles within a sluice box play an important part of this. A slower water flow might not keep a deeper riffle concentrating. A greater water flow can sometimes “boil-out” a lower-profile riffle. So as water flow is slowed down to catch finer-sized gold, it is generally necessary to use shorter riffles.

Half-inch mesh screen is commonly used for primary classification in small and medium-sized sluicing operations, because the screen is large enough to allow classification to take place quickly, yet no materials greater than half-inch in size will get into the sluice. Therefore a slower-velocity of water can be directed through the box, and fine gold recovery will be improved.

Classification for a sluicing operation can be done in any number of ways. One is to place a piece of strong half-inch mesh screen over a bucket, and shovel or pour through the screen into the bucket while sweeping the larger material off to the side. Once the bucket is filled with classified material, it can be poured into the sluice box at a uniform rate. It is better to not dump the whole bucket into the sluice all at once! This is because too much material is likely to overload the riffles and cause a loss of gold recovery.

In a situation where it is necessary to haul material a short distance to the sluice box, sometimes it is easiest to classify the material directly into a wheelbarrow and transfer only the classified material to the sluice.

Perhaps one of the best screening methods is to build a classification device that you can shovel into, and which will stand directly over the top of, and drop the classified materials into, the head of your sluice box.

The device should be built with the screen set at an angle. This way, larger material is helped to roll off of the screen as the pay-dirt is shoveled onto it. Smaller materials should fall through the screen and be directed into the head of your sluice box. This is actually a miniature model of the big classifiers used by large-scale heavy equipment bench-mining operations. A classification device such as this is rather easy and economical to build and will speed up a production-sluicing operation while screening is being done to improve gold recovery.

Any recovery system will only recover gold effectively down to a certain size-range. Most gold particles smaller in size than that will be lost with the tailings. Classification is one effective way of increasing the amount of gold that will be recovered out of the material that will be processed. As demonstrated in this following video segment, this is especially true of suction dredges; because dredges are able to increase the volume of production over other types of hand-mining activity.

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.