By Dave McCracken

A good challenge forces you to reach down deep inside and raise yourself to the occasion!

Dave Mack

The yawns being given off by my friend permeated the room so heavily that they clearly placed an uncomfortable shadow over the enthusiasm all the rest of us were feeling. We were on one of the most exciting treasure hunting expeditions I have ever been engaged in, and I was thanking my lucky stars just to be part of the expedition. All of the people involved were very good at their jobs and were enthusiastically involved with this project except my friend. He was bored. In fact, he was so caught up in his own personal boredom, that he was certain everyone else, and the whole world, was also seeing the world in the same mundane way. Talk about being on a different wavelength!

After our planning meeting was over, I gently approached my friend about his outlook. He agreed wholeheartedly with my observation. His viewpoint was because of some unknown factor that he could not quite pin down; he just was not able to take on the project (or life) with enthusiasm like the rest of us.

I asked if someone was sick in his family, or if he had financial or other personal problems that were holding him back. He said there was nothing like that holding him back. To him, for as long as he could remember, he was not able to experience real enthusiasm.

I don’t think any of us can expect to get more out of life than what we invest of ourselves into it. Wouldn’t it be wrong to take more than we give? How can we expect our passion to come from something outside of ourselves?

If we put passion in, perhaps we can get more passion and excitement out of it, whatever the endeavor.

My friend was waiting for some influence outside of himself to give him something to be passionate about. He was looking for some hidden reason why he was not feeling enthusiasm. I suggest that all of this might be a “backwards” approach.

I suggest the impact of life upon us (how we end up being affected by it) is exactly as we choose it to be. If we decide that the way we are going to feel most of the time is due to some (or lack of) outside or hidden influence or the way others have treated us (or not treated us) in the past, naturally, that’s the way it will be for us.

But it does not have to be that way. It can be any way we choose it to be. There are any number of responses we can choose for every given situation.

You do not have to win every battle to be a winner. If you win every time, you are not putting yourself to the real test. That’s not really winning, is it?

You do not have to be “rich” to be successful. Money is not life’s measuring stick.

Life must have worthwhile challenges for life to be interesting. A good challenge requires a fair chance (perhaps even likelihood) that you could fail in the endeavor. Real challenges make you fear the consequences of failing. A good challenge puts you to the real test. It forces you to reach down deep inside and raise yourself to the occasion. It makes you improve yourself. It makes you become more passionate, more brave, more tolerant of others and more secure in yourself.

A real challenge forces you to live life more fully!

I suggested to my friend that perhaps if he took on something more challenging he might discover his own personal enthusiasm. This thought brightened him up considerably.

Some philosopher once said that if taking on something is really difficult for you, try taking on twice as much. Then, the first limit you set for yourself will not seem like too much, anymore. There is certainly some profound wisdom in this philosophy. We do indeed set our own limits for ourselves by the decisions we make or the decisions of others that we agree to.

Ironically, my consistent observation has been that those people who are most challenged in their lives are happiest, most passionate and most enthusiastic even if there is a great deal of pain and misery in their lives. This is true in war-torn Cambodia. It is true in the remote portions of Madagascar where there is no medicine to save a sick child and where people work their guts out just to eat. In all their pain and suffering, those people really have passion in their lives. They are truly thankful for the little they do have. They are happy to be alive today. The few comfortable, good moments really have meaning to them.

“Perhaps we need the challenge of an occasional crocodile in our lives!”

Please do not misunderstand the point I am trying to make. I am not saying that pain and suffering are good. The point I am trying to make is that it is perhaps difficult to experience real passion and enthusiasm in our lives if we are so comfortable that the only adventure we experience is on the television.

Yes, we experience television with a passion. But what about life?

Perhaps, in the end, it is not about rich or poor — or about winning or losing. Just maybe, it is about experiencing everything out of life you can make happen. My guess is that this comes from putting in as much as you have to give. And that comes from being truly challenged in life, maybe even taking some chances.

We each set our own limits for ourselves. If we are not passionately trying to overcome those limits, then maybe we are cheating ourselves out of the best that life has to offer.

We easily forget this lesson in the West, where day-to-day life is not as dangerous as it might be. In many of the Third World countries I have visited, people have to face actual physical dangers in their everyday lives such as crocodiles. Let’s face it; there is not a lot of time to worry ourselves about petty concerns when we are concerned about getting eaten by a crocodile. Perhaps we need the challenge of an occasional crocodile in our lives!

 

 

BY ANTHONY “LITTLE TONY” STEURY, SR.

 

As usual, I awoke to the sound of a mother osprey’s loving shrieks giving instructions to her two young ones who had not yet mastered the art of flight. The sun was just coming over the top of Sugarloaf Mountain, quickly cutting the chill from the night air.

I could tell by the thundering sound of the rapids below my camp that the mighty Klamath River was rising at an alarming rate. The flood gates at the dam were being slowly raised, and I knew my time was limited. I felt that I must get down to bedrock under the rapids in order to find the gold that I knew had been waiting there for a gold dredger with modern equipment since the earth was formed millions of years ago.

As I quickly prepared a hot breakfast to help brace myself for the cold water I would have to endure, I reflected on the past two weeks dredging with my 6-inch dredge slowly moving yards of material, throwing cobbles, and moving small boulders to bore my way down to bedrock and get deep enough to escape the white water force that kept blowing me out of the hole. I was now at a point where most of the turbulence went over the top of my head, and I no longer had to work on my stomach with my face next to the nozzle intake to see. When I first started this hole, I was using 85 pounds of lead around my waist. One slight turn of the head would mean getting my mask or regulator ripped from my face by the turbulent force of the rapids.

I was snapped out of my interlude by the smell of burning bacon and a beautiful eagle gliding gracefully up the river taking full advantage of the thermal river canyon updrafts. Had I known then what events waited for me at the bottom of the river this day, I would have stayed in camp and dreamed of all the gold I had found in the years past.

As I put on my wet suit, my dog “Treasure” was already in the truck patiently waiting to go to our dredging operation as she had done so many times before. I think she knew our time was running out, and swimming the river to work our claim would soon be impossible.

I finished suiting up and grabbed all my gear. Twenty minutes later we were at the dredge, gassing up and getting ready to dive.

I took a quick look at my water marker, and it showed that the water had progressed 18 inches higher since yesterday. Not a good sign in the life of a fast-water dredger. Just as I started my engine and was preparing to slide down the suction hose into my hole, an ominous black cloud came from nowhere and totally blocked out the sun. It gave me a strange feeling as I looked up the side of the mountain and saw the old growth trees bending to a heavy wind by its awesome power. The cold, fast water slammed into my body.

As usual, my gallery was waiting for me in the bottom of the hole. Two ugly eels, three big suckers and many small fingerlings.

Without the sun, and because of a heavy flow of algae, it made visibility less then ten inches. I grabbed the nozzle and started plowing my way deeper around the base of a large boulder that I knew was lying on bedrock. Every day I had tried to move it with an 8-foot pry bar without success. “Today,” I vowed it would move. I threw caution to the wind and felt if I moved enough overburden from around its base, the force of the water would drop it on down behind me to the bottom tier of the rapids.

After steadily working for an hour and a half, I took a quick look at my watch and saw I had ten minutes of gas left. I was just about to go up and refill when the sun came from behind the clouds, allowing me to see that I had finally reached bedrock. There was a one-inch crevice starting at the base of the boulder making it a natural riffle. I took my small pry bar from my belt and pried into the crevice. Yes, I was right! Out came the gold into my suction nozzle. I had found the paystreak; I had outsmarted Mother Nature once again.

Just as I turned to go up and refill the gas tank on my dredge, I heard the familiar grinding sound of falling rock. A breathtaking pain shot up my leg causing me to spin around and grab my calf. As I did so, my mask and regulator were torn from my face. Experienced reflex made me grab my air hose to quickly retrieve my air source which I shoved back into my mouth, blowing out the water so I could breath God’s clean fresh air again.

At this point, after diving rivers and lakes clear back to when I was a young boy, I still panicked, causing me to hyperventilate. My mind started spinning to warn me I was about to black out. From out of nowhere, a voice was telling me to slow down my breathing, lie still and think things out before I became another one of the river’s many victims.

As my mind cleared, I started to run my hand down my leg, since without my mask, I could see only a few inches in front of my face. As I did so, again came the full force of pain which I was now more prepared for. After a quick search, my hand told me my ankle and foot were pinned under the large boulder that I had released with my foolish dredging around its base. I lay back again waiting for the pain to subside. Fighting panic, which would only bring me death, I took off one of my gloves and started to feel around behind me knowing my 8-foot steel bar lay somewhere near-hopefully close within my reach. It was the only chance of freeing myself, and a slim one at that. After groping around as far as I could reach, I was about to give up when my fingers touched steel. I arched my back and got three fingers around the point. Grabbing it the best I could, with my leg killing me, I pulled it toward me far enough to get a better grip and have total control. Just as I got it under and behind the boulder, I heard the engine stop from above.

I knew that there were only fifty-two seconds of air left in my holding tank. I twisted my body allowing me to put my unpinned leg against the boulder while, with arms above my head, I grabbed the top of the bar with both hands. I knew there would be only enough air for one chance to free myself. My mind raced back through my past. I thought of all the sporting events I had won in my youth. All the brave men who had died for their country telling me of all the things they still wished they could do. My family who still needs me and all of life’s battles I had won.

I felt a surge of power entering my body along with that gut feeling one always gets just before a win. I sucked in the last remaining air in my tank, pushing with my leg and pulling down on the bar with the 180 pounds of power that my body had to give.

Instantly, I fe1t the boulder move and I wrenched my leg free. Without hesitation, I ripped open my lead weight buckle release and shot out of the hole and down the rapids at breakneck speed.

In times past, this trip would mean a one-mile walk back up the river along a very rugged river bank, plus a one-hour delay swimming back across the river, floating down to my dredge, and retrieving all the gear I was forced to drop.

This day as my body was bounced along the bottom and slammed into boulders, I felt only the breath of joy while thanking a power greater than myself for this gift of life that was once again given to a mortal such as I. In a matter of minutes, my high-speed float trip was over, after being hurled into a slow water eddy which allowed me to drag myself up on a pile of cobblestones left by the old-time 49′ers.

As I laid back, totally exhausted from the pain and nerve-wracking experience, thinking about the fantastic gold deposit I had located, I looked up into the sky just in time to see my friend the eagle drop a wing tip to catch another updraft. He was, as always, looking after me and all of those who respect and love the river, saying farewell until another day dawned fresh in the life of the fast-water dredger.

 
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By Dave McCracken

“When to do a clean-up”

Some miners like to “clean-up” their sluice boxes after every hour of operation. Some prefer to do clean-up at the end of the day. Others will go for days at a time before cleaning up. This is all a matter of preference and seldom has much to do with the actual needs of the sluice box.

More commonly these days, a dredger only cleans-up the “high-grade” section of riffles in his or her dredge after each sample or at the end of a production day. That is a special small section of riffles which catch most of the gold near the head of the sluice. The full recovery system is usually only cleaned-up when enough gold has accumulated to make the effort worthwhile, or it is time to take the dredge out of the water.

There is a method of determining when a sluice box needs to be cleaned up, so that you can keep it operating at its utmost efficiency. If the majority of gold is catching in the upper-third section of the sluice box, then the recovery system is working well.

After a sluice box has been run for an extended period of time without being cleaned, the riffles will be substantially concentrated with heavy materials behind them. Sometimes an abundance of heavily-concentrated material in a sluice box can reduce the efficiency of the riffles. This is not always the case. Much depends upon the type of riffles being used and how they are set up in the box. The true test of when a set of riffles is losing its efficiency because of being loaded down with heavy concentrates is when an important amount of gold starts being trapped further down the length of the box than where it normally catches. When this occurs, it is definitely time to clean up your box. Otherwise, clean the box when you like.

Expanded-metal riffles, being short, will tend to load up with heavy black sands faster than the larger types of riffles. Still, a large, visible amount of black sand being present is not necessarily a sign that you are losing gold. Gold is about four times heavier than black sand. As long as there remains fluid action behind the riffles, the black sand might have little or no effect upon gold recovery. The best way to evaluate your recovery system is by direct observation of where the gold is being trapped.

DUMPING OFF

The concentrates which have accumulated in a sluice box can be removed by unsnapping the riffles, carefully removing the carpet underlay, and washing everything into a washtub or bucket. The contents can easily be rinsed out of the carpet underlay inside the washtub.

A medium-wide plastic putty knife can be very helpful in removing lingering concentrates from the high-grade section of a sluice box when that is the only place in the recovery system being cleaned-up.

The concentrates can then be screened into another wash-tub or into a bucket, depending upon what type of screens you are using. Classification of the concentrates into several sizes will allow you to process each more efficiently. The size-classifications that you want to use will depend largely upon how you will process the final concentrates. No matter how you process the final material, you almost always want to begin with a ½-inch or ¼-inch screen, just to eliminate all the larger-sized material from your concentrates. The following video segment demonstrates this preliminary screening, reminding you to carefully remove any gold nuggets which stay on top of the screen before discarding the larger-sized material:

There are several types of final clean-up devices on the market which can help you process the final concentrates, including different kinds of wheels, bowls and miniature sluicing systems. They all work pretty well when set up properly. Here is a video sequence demonstrating the use of a gold wheel to facilitate final clean-up:

Each device has its own instructions about the proper classification-size of concentrates for optimum performance. So you will want to buy or make your screens accordingly. The following video sequence demonstrates a second screening through a common sieve about the size of window screen – which is about normal for splitting concentrates into two sizes:

In my own operations, when we accumulate more than just a small amount of concentrates to clean-up, we have had very good results by first running the concentrates through a plastic Le Trap Sluice. First, though, we screen the concentrates through 8-mesh or 12-mesh screen to remove larger material. The following video sequence shows the Le Trap being used to help with a final clean-up:

Or, rather than use a special device (wheel, bowl, etc), you can work your concentrates completely or nearly down to the gold with the use of a gold pan. In this case, I would suggest that you first classify the material through 8-mesh (8 openings per linear inch) and then through 20 mesh (20 openings per linear inch) screens to break it up into three sizes: 1) the material which stays on top of the 8-mesh screen; 2) the material which passes through the 8-mesh screen but stays on top of the 20-mesh screen; 3) and the material which passes through the 20-mesh screen.

Under normal circumstances, the larger two classifications of concentrate will pan down to gold by themselves quite fast. Because of this, even a final clean-up device is usually only used in the field on that material which will pass through the smallest classification screen.

I have thoroughly demonstrated the panning process in a separate article, so I won’t repeat that here.

FINAL DRY SEPARATION

These final clean-up steps can be done at camp, preferably in a dry environment, where the wind is not blowing much and where there is a table top or some other flat surface available to you for a work space.

Important: Before you do the first step of this process, it is best to work your concentrates down as far as possible, to remove all of the black sands that you possibly can. The more black sand you can remove while the material is wet, the less you have to deal with after it is dried. Sometimes you can remove more black sand with the careful use of a finishing pan (small steel gold pan about 6-inches in diameter) inside of a small wash tub.

A Gold Extractor will allow you to work all of your gold down with no loss, and only about a tablespoon of black sands remaining.

Important Note: The best finishing device I have ever seen for working concentrates down to only about a tablespoon of remaining black sand, with zero loss of your gold, is called a “Gold Extractor.” Once your final concentrates are worked down to a very small amount of black sand remaining, you are ready to go on to the next step.

STEP 1: First dry out your final concentrates. This can be accomplished by pouring them into a small metal pan (finishing pan is best) and slowly heating them over an open fire or gas stove-whichever is at hand.

Dry out the concentrates.

CAUTION: Heating the concentrates from a gold mining program should not be done inside of a closed environment. Heating should be done outside and/or in a well-ventilated location, where any and all vapors given off by the various steps will be swept away from you and other bystanders.

You do not want to heat the concentrates too much at this stage. This is because they may still contain some lead. Excessive heat can melt the lead onto some of the gold within the concentrates. Pay attention to heat just enough to thoroughly dry out your concentrates. Be careful that boiling or bubbling during heating is not allowed to spatter gold out of the pan. The following video segment demonstrates this step:

STEP 2: Once the concentrates have cooled enough that they can be handled, they should be screened through a piece of window screen (about 12-mesh). A small piece of window screen, about 6-inches square, is handy to use for this purpose.

STEP 3: Take the larger-sized concentrates (the material which would not pass through the window screen), and pour them onto a clean piece of paper. If there is a lot of this sized concentrate, this step will have to be done in stages, handling a little at a time. Once the concentrates are poured onto the paper, it is easy to separate the pieces of gold from the impurities. The impurities should be swept off the paper and the gold should be poured into a gold sample bottle. This is where a funnel comes in handy.

STEP 4: Once the larger-sized concentrates have been separated, the remaining concentrates can be classified through a finer-mesh screen. A stainless steel, fine tea strainer (about 20-mesh) works well for this. Tea strainers can be found in just about any grocery store.

STEP 5: Take the larger classification of concentrates from the second screening, pour them onto a clean sheet of paper, and separate the gold from the impurities in the same way that it was done with the larger material in Step 3 above.

Use of a magnet on each size-classification of concentrates can be very helpful to remove those impurities which are magnetic.

Some prefer to use a fine painter’s brush to separate out the non-magnetic impurities. Separation can also be accomplished by using your fingers. This step goes faster if you only do small amounts of concentrate at a time. Pour the gold recovered in this step into the gold sample bottle.

STEP 6: Take the fine concentrates which passed through the final screening and spread them out over a clean sheet of paper. Use a magnet to separate the magnetic black sands from these final concentrates. The magnetic black sands should be dropped onto another sheet of clean paper, spread out, and then gone through with the magnet at least one more time. The reason for this is that some gold can be carried off with the magnetic black sands. They tend to clump together. Once the magnetic black sands have been thoroughly separated from the gold to your satisfaction, pour them into your black sand collection. There may still be some small gold values left with them which can be recovered by other methods at another time.

NOTE: There is a really nice set of final clean-up screens on the market that are made just for the purpose of separating your final concentrates into the ideal size-fractions for final dry separation. I highly recommend them, because they separate your final material into multiple size classifications which make the final dry process go even faster.

STEP 7: Now, all that should be left is your fine gold, possibly some platinum, and a small amount of non-magnetic black sand. These final black sands can be separated by blowing lightly over them while vibrating the sheet of paper. Since the sand is about 4 times lighter than the gold, it will blow off the paper a little at a time, leaving the gold behind. Once all the black sands are gone, you can pick out the pieces of platinum if present, and separate them from the gold. Pour the gold into the same gold sample jar used in the earlier steps.

This dry process (Steps 1-7) goes very quickly if an effort was made during the final wet stages to get as much black sand and other waste material as possible separated from the gold.

CLEANING GOLD

Sometimes placer gold just out of a streambed is very clean and shiny. If this is the case with your gold, after the final dry cleanup procedure is completed, your gold is ready to be weighed and sold or displayed or stored away in a safe place.

Sometimes, gold will come out of a streambed with some impurities attached to it. When this happens, it will be necessary to perform a final cleaning process to make the gold’s natural beauty stand out.

If your gold is not clean and shiny, and you want to get it that way, place it in a small non-breakable water-tight jar about half full of water and add a little dishwashing liquid. It does not seem to matter what kind is used. Fasten the top on the jar and shake the contents vigorously until the gold changes to somewhat of an unnatural glittery color. Sometimes this happens quickly and sometimes it takes a little longer. This mostly depends upon how much gold is in the jar. The more gold, the faster the process. This is because it is the friction of gold against gold which facilitates the cleaning process. Once the gold is glittery, rinse the soapy water out of the jar, pour the gold into a small (metal) finishing pan, and heat it up (outside and down wind) until the gold takes on a deep, natural, shiny luster. It is important to make sure that all of the soap has been rinsed away from the gold using clean water before you dry the gold.

Gold has a tendency to turn a dull color after having been stored in an airtight container for an extended period of time. For this reason, some gold miners and dealers store their gold in water-filled jars, and dry it out just before displaying it or making a sale.

If you should happen to store your gold in an airtight container and notice that its color does not seem to be as bright as it once was, wash it with soap and water and re-heat it, as in the above steps. This process will bring back the beautiful color and luster of the gold.

The best time to weigh your gold to get the most accurate measurement is after you have completed all of the final cleanup steps.

SELLING GOLD

There are numerous markets where you can sell your gold. Refineries will pay you for the fineness (purity) of the gold itself and subtract a few percent for refining charges. In this case, you will receive a little less than the actual value of the gold. Refineries usually will not pay for the silver and platinum contained within your placer gold unless you are delivering it in large quantities. Refineries prefer that you bring your gold to them in large amounts. They will often charge less for refining, and sometimes pay just a bit more for the gold, when it is brought to them in larger quantities.

Flakes of gold and nuggets have jewelry value on a different market. If marketed to the right buyers, flakes and nuggets can usually bring in more than a refinery will pay-or sometimes even much more.

If you are in gold country and ask around, you can nearly always find someone who is buying placer gold from the local miners. These individuals usually pay cash. Unless the fineness of the gold within the area is lower than normal, there is no reason to settle for less than 70% of the market-value of the gold for that day. This means that the gold is weighed and the buyer pays you for the weight of what you deliver. Impurities are never calculated into this type of deal. If you enquire around, you can usually find someone who is willing to pay 75% of weight. Sometimes you can find an 80% straight-out buyer-which is good.

There are also people out there who are ready to gyp you out of your gold if they can get away with it. It is wise to bring your own pocket calculator along when dealing with a new buyer.

If you go to a dealer who starts figuring a certain percentage of the fineness, and his final figures end up lower than a straight out 70% of the bulk weight of your gold as it is, go find another dealer. This is not to say that 70% is the going rate. You can do better if you look around. Although, you should never have to accept less than 70% of the going market price for your gold. If a dealer starts to tell you all sorts of reasons why your gold is not worth what you want for it, go find someone else. There are plenty of gold buyers around who will at least admire your gold. So there is no reason to hang around and listen to someone who is trying to steal it from you.

Local miners will know who pays the most! Or go up on our web forum and ask. Someone there is sure to turn you onto a good deal!

Cleaning your gold well before you take it somewhere to be sold can help a lot.

Sometimes dentists will give you a good price for your gold, and a phone call or two can pay off. Also, some lawyers and businessmen like to invest in gold. Sometimes you can get up to 100% of spot for your fines (fine gold) when dealing with them.

Some jewelers will pay well for your flakes when they have a demand for them. It is not uncommon to get as much as 90% or better when you make such contacts.

The best way to get top dollar for your gold is to do a lot of inquiring, always with the intention to find more and better markets. Then, when you need some cash, you can sell to the buyer who pays the most.

 

 

It is getting pretty close to dredging time, and if you are anything like me and the many other dredgers I know, you are probably just itching to get started.

My partners and I, from past experience, now spend the necessary time and energy, before the dredging season starts, in getting all of our equipment repaired-to avoid the otherwise often confrontations with Murphy’s Law.

Some of the standard things we go through are as follows:

Engine and Pump: We always replace the spark plug, motor oil, points and condenser and air filter at the beginning of every season. We also pull the pump impeller to make sure it is not worn or damaged, and to make sure nothing is lodged in it. And we check the pump seal and replace it if it looks the least bit worn.

Air Compressor System: All of the compressors I have seen on gold dredges have reed valves. These are stainless steel plates which allow air to only flow one way through a chamber. These reed valves ought to be cleaned, polished and straightened at the beginning of every season. Some compressors have rubber diaphragms and some have piston rings. These ought to be checked and replaced if necessary. Rebuild kits are generally available for each type of compressor-usually from your local prospecting equipment dealer.

We always open up our regulators and blow them out with compressed air. You will want to check to make sure there are no holes in the rubber diaphragm, and make sure the rubber exhaust seal is working properly. If you have problems with water getting inside your regulator, it is almost always because of a worn out rubber exhaust valve. These are easy to obtain and replace.

It is especially important to open up and clean any check (one-way flow) valves in the air system. We also always soak our air lines in a very mild bleach-water solution before starting a season. We let the airline sink in a tub of the solution to allow the bleach to kill off any fungus which has grown inside the airline. This is to avoid potential respiratory problems from the fungus. The line needs to be thoroughly rinsed with fresh water afterwards.

We check all of our airlines and fittings to make sure everything is working properly-no leaks, and no weak connections!

We thoroughly clean out our air reserve tank to make sure there is no rust, fungus or other substances which could potentially cause problems.

Dredge (Structural): And, of course, we go over the sluice boxes, dredge frame and jets to make sure there are no holes, cracks or other structural problems. And if we find problems, we fix them on the spot. No need to wait until it becomes a more serious problem during the season.

We hit all of the steel with a wire brush and follow up with a fresh paint-job every spring. It’s nice to start the season off looking good!

We go through all of our rope and make sure all of the weak points are cut out and spliced back together, and all of the ends are spliced or melted so there are no frayed ends.

Diving Gear: We go through all of our diving gear, replacing anything that is worn out, patching holes in suits, etc. No need to be any colder than necessary during the early spring!

While fixing up the dredging equipment is not as good as using it, I personally gain a great deal of satisfaction getting it all prepared for the season. And, it’s always a good feeling when I do get out on the river when I have it all together the way it should be. And when “Mr. Murphy” comes knocking at my door, at least I know it wasn’t because I failed to plan ahead.

 

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.

 

 

BY PAUL BADALI

Since we’re still in the mainstream of the dredging season, I’ve decided to share a few tricks I’ve picked up in my experiences with dredging over the past few years. Hopefully they will help to make your dredging a little easier.

After several seasons of use, dredge hose becomes cracked and needs to be replaced. I have tried to repair the cracks and holes in my 5-inch yellow hose with silicone R.T.V. glue, that didn’t work; so I knew I would be replacing it. The only 5-inch hose I could find in the dry desert state of Utah was a very light duct hose called Spirolite, which is used to blow insulation into attics. The hose is so light and thin that I decided both the first and second time I went in to purchase some it could not hold up under dredging conditions. But the price was so good (about $3.90/foot for 5-inch) that I finally bought a 10 foot length just to see how it would hold up in the Klamath River. I liked it so well that when Tony Dilmore, who had originally recommended it to me, showed up in Happy Camp with some, I bought another 20 foot length from him.

Spirolite has definite advantages in some dredging applications. First of all, it is extremely flexible. It is ideal for creek dredging where the hose often must be wrapped around boulders. Secondly, it is extremely lightweight weighing only about half what the yellow hose weighs, so it’s easier to pack down the bank or into remote dredging sights. It does not show excessive wear as I had feared it might. When I first looked at this hose, I pinched my thumb nail and finger nail together on the thin clear material between the spiraled ribs and was able to pinch a hole in it. But I can’t see any holes in my 20 foot section of hose after half a season’s use in the Klamath River. So, it seems to hold up well. It does develop small holes where it is clamped to the nozzle and the jet, but these areas are at the end of the hose and can easily be cut off when they get bad. And at $4/foot, you can afford to take this into account and buy five feet more than you need. And as for beating out plug-ups, you don’t have to. This hose is so flexible that it rarely plugs-up. If a rock does turn sideways and plug, you simply deform the hose with your hands, and the plug frees with no hammering on the hose!

There is one application where a heavier, stiffer hose is preferred over the Spirolite, and that is in deep or fast water. Because the hose is so light and flexible, the water can grab it and keep pulling it out of your hole. When I used this hose in the gut of the “Glory Hole” on the Klamath in about 15 feet of water, I had to keep the dredge near the edge of the river, use 30 feet of hose, and anchor it to the bottom at two points on the way out into the gut. The nozzle still washed out each time I went up to knock a plug out. But for calmer more shallow water, it’s the hose I prefer to use.

You should be able to get it at most large hose supply stores in larger cities. If they don’t recognize the brand name Spirolite, ask for the lightweight clear spiral duct hose they use to blow insulation into attics with, and get prices at three or four hose supplies. You may get it even cheaper than I did!

Has your swivel nozzle stopped swiveling after two seasons of use? Mine had. Sand and small rocks work their way down into the joint, and rust accumulates in there over the winter. But if you have access to an arc welder, the repair job is simple. Just cut or grind off the weld beads that hold the swivel joint to the nozzle, and remove the swivel joint. Inside you will find two rubber O-rings or pieces of rubber cord cut to work as O-rings. Pull the whole assembly apart, and use a wire brush to buff rust and sand off of all the metal parts. Clean the rubber cord or O-rings in water.

You want to catch any sand that falls out, and pan it. I found one nice flake of gold inside my nozzle when I cleaned it. You may wish to use some type of non-oil lubricant in the swivel joint before you reassemble it, such as graphite or silicone. I haven’t done this yet, but I suspect graphite is the way to go.

To reassemble, simply match the old ground-off beads back up, and tack it in the same spots with an arc-welder. I would not gas weld these beads, as I suspect it would get the rubber O-rings too hot and damage them. When you are done, your nozzle should swivel as good as new. While you have the welder in hand, touch up any wear you see elsewhere on the nozzle.

This last winter, I got about 26 feet of 36-inch-wide miner’s moss free! You may be able to do the same. I noticed that miner’s moss was used on the floor as mats in every entrance at a local high school. I found the janitor and asked if he would keep me in mind, and give me any old pieces he might be throwing out in the future. He was curious as to why I would want old mats, and we got into an hour’s discussion about dredging for gold. At the end of our chat, he said, “You know, I think we have a few old pieces we’re throwing out in a store room right now.”

We went to look, and he helped me wheel out three six-foot pieces, and one eight-foot piece of miner’s moss. They needed some cleaning up, but hanging the carpets on the kid’s swing set and using the garden hose soon took care of that.

The moral of this story is ASK. If you want something, ask. If you think people will say no, nine times out of 10, then just ask 10 people, and you’ll get what you want. Everyone has seen miner’s moss being used for foot mats. The U.S. Postal Department uses it, supermarkets do, banks do, etc. They all have to throw out the old and replace it with new. So ask for the old mats, and chances are you will get some!

I would also like to give some advice on moving your small-size dredge around on a big river like the Klamath. If you are not a good swimmer, and you are scared to death to swim across; then listen to your intuition, and stay on the side you’re already on. Know your own limits, and don’t get yourself into trouble. But, if you’re an average swimmer, and just a little apprehensive, then here are some tips on getting yourself, the dredge, gas supplies, and concentrates back and forth across the river without a boat.

Number one, buy a good set of fins. Good fins fit over your wet suit booties and are fairly stiff. They are not so stiff that they feel like cedar shingles, nor so soft that you can touch the tip of the fin to the heel, but somewhere in between. With a good set of fins, you have about as much power in your legs as a 2-hp outboard motor, and you can really cruise across that river! Always wear your wet suit without weights when crossing, and take it easy. If you’re not used to pumping fins, you can quickly get a leg cramp from over exertion.

The current will pull you downstream as you swim. Pick a calm stretch of river to swim across, and start way up stream from where you want to end up. Don’t choose a calm spot immediately above bad rapids, because if you don’t make it, you will be going for a very bouncy ride. If you are crazy like I am, this can be lots of fun, but it can also freak out your wife who watches the ride from shore!

To swim across, just float on your back, point yourself towards the other shore, and pump your legs. Don’t try to head up- stream and fight the current! Just start way upstream from where you want to land on the other side, and take a relaxed ride. The fins do all the pushing, just let your arms dangle. With fins and a wet suit on, it’s easy as swimming in a lake.

To take my dredge across, I load everything onto it, and push on the tail-end of the sluice box while kicking with my fins. I do not like a rope tied from the dredge to the shore. I do not swim a rope across first, and let that rope pull the dredge in. I play outboard motor with my fins, and I propel the dredge to the other bank. I lie on my stomach if pushing, or on my back if pulling. I feel much more in control of the dredge this way. I do choose a very calm stretch of river to do this, and I give myself twice the distance upstream that I think it will take to get across. It’s easy this way for one guy to get a dredge across by himself, and it’s a breeze if you have a helper also wearing fins.

Supplies and concentrates are also easy to get across. If you use a large 30-gallon tub to dump your concentrates into, you already own a small boat. You can put your weight belts, winch, tools, towels, etc. into the tub, and pull it with you as you lie on your back and kick across. It will sink if you tip it, and an inflated inner tube around the tub adds safety and more buoyancy. You can pull people in dry clothing across in a small rubber raft as fast or faster than they can paddle. You can also very easily swim a motorized sluice (high-banker) across the river in a small raft or an inner tube. You can fit lots more cargo in a rubber raft if there is no one in the boat! Obviously, when you want to come back across the river, you have to walk upstream; because you will be washed downstream as you swim back across.

There really isn’t much to fear from a big river if you are careful. You float like a cork in a wet suit. Don’t fight the current! The current is stronger than you are, so “go with the flow,” and let it work for you. Get good fins, so you have some push, and have a good time with it. In most cases, there has been less prospecting and mining done on the other side, so you may reap great rewards for your investment in a pair of good fins!

Good luck, and see you out there!

 

BY SAM LONG

 

Dry-washing, in many ways, puts me in mind of eating at a Chinese restaurant with chopsticks. It’s fun to try; but you can’t move material from one place to another very fast, even if you’re good at it. That’s why it’s so important to pick out an area with a theoretically high concentration of gold. Of course, down here in Arizona, you’ve got about as much chance of finding an area like that as a one legged man’s got at winning a kicking contest!

That’s not to say you shouldn’t try. I always do so with this theory in mind: Billions of years ago, when God was putting tons of gold in Alaska, South America, Russia, Australia, the Yukon, and even California, he accidentally spilled a couple of pounds over Arizona. I always think of that after I’ve worked through a pile of rocks and sand big enough to shade an elephant, and not come up with enough gold to fill a tooth. All the expert mining techniques in the world won’t come up with a speck of gold where there’s none to begin with. So, the place to start is history.

I know you’ve read it a thousand times. Now you can say you’ve read it over a thousand times: It’s usually better to begin your search for gold in an area that has produced it in the past. The more the better.

From that point, go to maps. Study them religiously. I take my topographical maps to an office supply that has an enlarging copier. I have the section I’m interested in blown up two or three times. This really helps in seeing all the side washes, forks, bends, and places of slowing water that are the obvious holding spots for gold.

Now, you’re ready to hike to these areas. Of course, on your way to and from these spots, keep your eye open for any likely looking area you might have overlooked on your map. There are a zillion of them, so you’ve got to learn to be very selective.

Remember, you want to shovel rocks, sand, and gold through your dry-washer, not just rocks and sand. It doesn’t matter to your shovel. It doesn’t matter to your neighbor. It only matters to you. Take your best shot before you ever crank up your machine, and you won’t have to deal with the disappointment of getting skunked.

And, just how do you do this? Sampling. That’s right— sample, sample, sample. If you’re diligent about it, and do it correctly, when you finally start dry-washing, your question won’t be will I find gold? It will be how much will I find?

Starting up your dry-washer in a likely-looking spot without sampling, makes about as much sense as a dog barking at a knothole. Sure, sampling is a lot of extra work and it takes time. But, when it’s all said and done, you’ll end up with some gold along with the new blisters–instead of a sour attitude and the new blisters.

This isn’t to say you can’t set up anywhere and get some color. But to my way of thinking, that would be pure luck; and I haven’t experienced enough of that to feel qualified to write about it. If you have, and can make it work time and time again, I’d sure be willing to learn.

So, here we are in a gold producing area, walking up a wash that had some likely-looking gold-holding spots on our map. How do we sample? Well, as with most things, there is more than one way to skin a cat. I use a Goldspear. It’s proven itself to me to be an accurate, time saving, prospecting tool. I know lots of folks don’t think much of them, but usually they haven’t ever owned one, or don’t understand how to use them to their advantage. Granted, they’re not some super tool that can automatically find gold. But used correctly, they can sure save you a lot of needless digging. And, at the price of shovels these days, you don’t want to wear out any more than necessary.

For now though, I’ll skip the use of the spear and explain a few points of how I sample without one. Again, this isn’t the only way to sample or dry-wash, but it works for me. Adapt it to your own personality and tools, as you see fit. In my pack, my basic tools are: Two pans, a small kitchen sieve; and, because we’re prospecting dry washes, a wide-mouth plastic gallon jar of water. Needless to say, never go anywhere without your rock pick.

With these basic tools, slowly work your way up the wash, visually sampling as you go. In your mind’s eye, continually look for the places gold is likely to accumulate. The more of these types of places you can recognize, the more success you’ll have in sampling.

Likely gold-holding areas would be the inside of sharp bends; areas where the wash levels and widens, indicating slowing water; areas of red and blue clay; pockets of iron pebbles, which show the water’s inability to carry heavier minerals; or a zone of magnetite, hematite or quartz. All these are good visual indicators that gold will likely be present.

After finding a place containing as many positive indicators as possible, roll over the biggest boulder you can in that area; and using one pan to hold the water, screen some material from under the boulder into the other pan and go to work. If you’ve done your homework right, this should yield you a few colors. Jot down how many on your map at the place where you found them. If more than just a few colors materialize, try a couple more pans before moving on. Continue in this manner for the rest of the day. You should have a few different areas that are somewhat better than the others.

Now that you’ve picked a good spot to work, and packed in all your equipment, the last important point is the speed at which you run the material through your dry-washer. It’s a big temptation to drop your riffle board too low so you can process material faster. But by doing this, you’ll lose a lot of finer-sized gold. As you either know, or will soon find out, most gold in the dry washes is very small. Unless you keep your riffle board only slightly lower than level, a good portion of the fine gold won’t have time to settle. It will end up going over the end instead. You can’t feed any more material in than is going out, so be careful not to overfeed the hopper. Otherwise, you’ll end up with gold in your tailing pile. Nothing will make you feel ankle high to a frog in a post hole quicker than your neighbor coming by, to run his Goldspear through your tailing pile, and getting enough beeps to make a liar out of you, when you tell him you were planning to run it through again a second time anyway.

The biggest hindrances to running your machine are laziness and rain. If you’re the type who does more spitting on the handle than shoveling, you’ll probably welcome the rain. If not, the folks around you will surely think you were raised on sour milk. It takes the fun out of dry-washing when you just get going good, then it rains and stops your operation. That’s what happened to us this winter. With my Keene dry-washer, I could work wetter dirt than everyone else because it blows hot air. But after the fourth cloudburst, it was even too wet for me. We switched it to a re-circulating water system and kept going.

So, if you pick the right spot and don’t push your machine, you’ll get some good gold. It might not be the most gold you’ll ever get in a day, but that desert-gold is some of the prettiest you’ll ever find. Since gold is more ornamental than useful anyway, you ought to be happier than a fly in a raisin pie

 

By Jimmy Sierra

“What goes on in that metal box may be a mystery to most of us, but we all know it isn’t magic”

 

Metal detectingThe title of this article can mean different things to different people and thereby add to the mystique surrounding the entire field of metal detecting, for that is what “Electronic Treasure Hunting” is all about. The word electronic should mean the same to everyone. What goes on in that metal box may be a mystery to most of us, but we all know it isn’t magic.

The vast assortment of transistors, resistors, capacitors and various integrated circuits add up to a very sophisticated type of transmitter which broadcasts a signal through the transmitting coil of copper wire contained in the disc or loop at the front-end of the detector. This signal is affected by the electromagnetic field which is present around all metal objects. Thus, when it returns to the receiver-coil in the loop, this signal is changed. The change is interpreted by the complex circuitry in the detector box and lets us know that there is metal out there.

Depending upon the sophistication of the detector, this data can include the possible type of metal, depth of the item and even the shape or identity of the metal object. This may be an over-simplification of what goes on, but we need not worry about how it happens. Let the engineers who invent these devices handle that. The thing to remember is, metal detectors find metal. There are variables that create differences between detectors, and these variables will determine which style of detector is best-suited to the type of treasure hunting that we wish to do.

This brings us to the second part of the title of this article: Treasure Hunting. As I mentioned, this is the part that means different things to different people. To some, it means looking for dropped coins or jewelry in various places such as parks, playgrounds, backyards, beaches, picnic grounds or even old ghost towns. The locations change and the technique for searching varies a great deal, but the basic function of the detector to locate metal is the same. Some consider treasure hunting to be locating caches of buried coins or valuables, even sunken galleons. Again, the treasure and the location change, but the detector is still operated as it is de- signed, to locate metal objects.

To others, treasure hunting takes the form of searching old battle sites or ghost towns for relics of days gone by.

And yet, another select group of treasure hunters who call themselves “prospectors” direct their search for the elusive nuggets of gold, long sought by man to be used as a measure of wealth.

By now I hope it has become apparent that the common denominator linking most treasure hunters together is the electronic metal detector. The location may change and the targets may differ, but all respond to the initial function of the detector to find metal. It is only necessary to vary where we look, and to some degree, develop special skills unique to each type of treasure in order to change from coin shooter to cache hunter to relic hunter to prospector.

This might be a good time to clear up one particular misconception, one that has been brought to my attention hundreds of times over the years by those unfamiliar with treasure hunting. That is, the idea that metal detectors cannot find GOLD. This stems from some misunderstanding about the nature of gold. When I have questioned these people, I have found that most were not really sure if gold was a metal or not. Some had a vague idea that gold might be classed as a mineral. Most, however, were not sure what the difference was between a metal and a mineral.

In brief, the difference between a mineral and a metal is that a mineral is a chemical compound of more than one element, and a metal exists in its pure state as a single element. So, let’s just accept the fact that iron, copper, lead, silver, and GOLD are all metals and can be found free in that form, and that all of them can be located with a metal detector. We can surely begin to see why such mystery surrounds gold and gold prospecting, as well as treasure hunting in general.

I do not mean to imply that electronic treasure hunting or prospecting is as easy as falling off a log; only that it is not magic, and that the skills acquired while learning to hunt coins in a park with a detector are the same skills used when prospecting for gold nuggets in the Mohave Desert. The target and the location change, but the basic skill is only varied by the different types of hunting.

Up until several years ago, one of our most successful coin shooters from the Sacramento area in California had never seen a gold nugget except at the various gold shows where suction dredgers show off the treasures which they find at the bottom of streams and rivers. He had acquired the necessary skills over the years in the operation of his detector. He had learned to utilize the ability of his detector to cancel-out the ground mineralization caused by iron ore and salts which mask the ability to locate metal objects such as coins. He had trained his ear and slow searching techniques to hear those deep older coins. When he decided to give a shot to gold prospecting, he had little else to learn. He was successful right from the start. Of course, he didn’t look for the nuggets in the local park. But, he did find his first nugget in a dry streambed not more than 15 minutes from his house. He was bitten by the gold bug on that first day and will never be the same!

His biggest problem was to find a good place to hunt. He rightly concluded that the best place to start was where the old 49ers had found gold. If it was there then, it was surely there today. He was right. He began by going over the tailings left behind by old-timers. Gold was plentiful and the old methods of recovery were not perfect. Carelessness and lack of skill left plenty behind. He researched old maps and history books to seek out previous diggings. Sometimes, he went over old tailings. Other times, he searched dry washes and gulches near the diggings. Experience sharpened his skill and techniques, just as those many hours spent in the old parks had prepared him for this new approach to treasure hunting.

Averaging three days per week searching, he found more than 40 ounces of gold last year!

I do not want to paint too rosy of a picture here. The fellow mentioned above is a real experienced detectorist. He spends time hunting and looks for the right spots. Few of us will measure up to his success. But most who try their hand at treasure hunting will be pleasantly surprised at how fast they can become skilled in the use of this electronic device. Practice and patience are all that are required. Skill in tuning and operating the detector comes from reading the manual carefully and asking information from the dealer that sold the unit. Other users are a good source for acquiring special helps in learning to use the unit. I, as well as others, have written articles and books explaining in detail the tuning and searching techniques of metal detecting.

Joining up with others in a Club or association will gain you very valuable access to experience and places to hunt for golden treasure.

One of the unpredictable ingredients in the creation of a successful treasure hunter is LUCK!! The old adage that you have to be standing over a target to find it, is true. My friend and I were searching an old baseball field a number of years ago which was adjacent to an old Mission. We both found numerous coins, many silver, but all from this century. I was lucky enough, however, to find a 1778 Spanish half real dating back to the Mission Period. It was only 4 1/2 inches or so deep. It was luck. I was practicing the same learned skills as my partner and we both were successful. My old coin was there because I was standing over it.

I have a good friend with whom I prospect. We dig a lot of targets in order to find the elusive gold nugget. I have found many nuggets, most in the tiny-to-small size-range, but none really large. However, along with many smaller nuggets, this fellow has found a 6-ounce, a 9-ounce, and a 12-ounce piece of Mother Nature’s natural golden treasure. Granted, he hunts for gold nuggets a lot more than I do, but many who hunt as often as he does never find nuggets in that class. Wouldn’t you say some luck came his way? Each one of these nuggets was found with a different make and model of detector.

Many detectors are pretty equivalent in ability to find metal, but all metal detector users are not equal in skill — or in luck.

Another example comes to mind at this time: This one might seem pretty far-fetched, but it is true. A few months ago, a prospector-friend of mine called to announce that he had just found his largest nugget to date. It was a ¾-ounce piece, that’s 15 pennyweight. Now, that is a respectable nugget. Of course, he said he found it with the help of his faithful dog. You might call the dog his gold-hound at this point. While my friend was prospecting along the bank of a popular river, his dog was doing his duty near the water. As he noticed his dog scratching at the sandy shore, he caught a glimpse of something flashing in the sunlight. He went closer to investigate and spotted the aforementioned nugget with loop and all attached. Some luckless prospector had lost his prized specimen from around his neck. One man’s loss is another man’s gain, as they say. It goes without mention that this is one dog that will never want for attention again!

We have talked about learning how to use the detector, regardless of what the object of your search is. There is no substitute for expertise and skill. We have mentioned that buying the proper detector is essential and we have pointed out that a certain amount of good luck doesn’t hurt. The final ingredient is good old perseverance and perspiration.

My basic intent in this article is to clear away some of the magic from electronic metal detecting and show it as an acquired skill, which is what it really is. It is important to buy the best detector you can; one that has the ability to cancel the ground-mineralization. This is most important if you plan to use the detector for prospecting, because gold and silver are most-often found in highly-mineralized soil.

If you are going to use the detector in trashy areas (lots of man-made metal objects), you should buy a detector that has some ability to identify trash. Otherwise, you will have to dig every target that sounds off. This is not only tiring; but since you can only dig so many targets in a day, it diminishes the odds of digging good targets. You can see that this would not be important if you were relic hunting, where all items are potential treasures. But it is more important when coin hunting, where pull tabs and bottle caps are not desired, or in prospecting, where nails and tin cans left from former miners are tedious to dig and not as valuable as gold nuggets. Of course, if the area is virgin, one would not have a need for identifying trash.

Being able to identify a “hot rock” (a rock with different mineral content than the surrounding terrain) is also an important feature to be looked for in a detector to be used for prospecting. Have your dealer help you pick a detector best-suited for your needs, whether they be specialized or multi-purposed.

Good Hunting!

 
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By Dave McCracken

Always set up a dry-washer downwind of where you are working!

Dave Mack

 

Deserts consist of huge deposits of sedimentary material which have been affected by ancient ocean tides, ancient rivers, glaciers, floods, gully washers and windstorms. They are literally a gold mine of placer deposits.

There is also an enormous amount of gold-bearing mountainous dry placer ground which has remained relatively untouched by large-scale gold mining activity because of the scarcity of water required in those locations to support wet recovery methods.

Generally speaking, dry methods of gold recovery are not as effective or as fast as wet recovery methods. Yet, dry methods do work well enough that they can produce gold well if the ground is rich enough. Recent developments in dry washing equipment have made it possible for a one or two-man operation to work larger volumes of dry placer ground without water, and obtain good results in gold recovery.

Dry processing recovery systems generally use air flows to do the same job that water does in wet recovery systems. Under controlled conditions, air flows and mechanical motion and vibration can be made to effectively get rid of lighter, worthless materials. This causes a concentration of heavier materials similar to what occurs in wet processing.

SETTING UP TO WORK AN AREA

Sometimes a road can be bulldozed to your spot. Sometimes you can drive right in with a 2 or 4-wheel drive truck. In these situations, you might consider screening pay-dirt into the back of a truck and hauling it to a wash plant to be processed elsewhere. Actually, this is just slightly more difficult than shoveling directly into a wash plant. The hardest part is breaking the material away from the streambed and classifying it. It takes a little more time to haul the material to the wash plant, but that depends upon the distance and the condition of the road. It is also more difficult to shovel up into a truck. Some small operations use a portable conveyor belt to lift the material into their truck. Feeding the material from a truck into a wash plant is not as difficult, because it is usually down hill. An average one or two-person team should be able to move the equivalent of a pickup-sized load of screened pay-dirt and process it through a wash plant at another location in the period of a full day’s work-perhaps even two truckloads, depending upon the distances involved. If the material is paying well, they could do well at it, too.

DRY-WASHING PLANTS

If conditions do not allow you to truck the pay-dirt to a nearby water site to be processed by wet methods, you will have to consider processing the rich material by dry-production methods.

While dry-panning and winnowing do work, and have been broadly used as a means of production during the past, they are not normally as effective as some of the modern dry-washing plants which are available on today’s market.

Dry-washing machines use an air blowing fan or bellows-type device to blow a controlled amount of air-flow up through the dry material that is being processed. Air flows help blow off the lighter materials and allow the heaviest particles and gold to collect.

Dry-washing plants are available which can either be operated by hand or by lightweight engine and air-fan assemblies.

“Non-motorized dry-washing unit”

A hand-operated dry washing plant usually includes its own classification screen as part of the unit. Raw material can be shoveled directly onto it. The bellows air-blower is usually operated by turning a hand crank, which is often conveniently located so that one person can both shovel and alternately work the bellows at the same time. Under ideal conditions, two people working together can process up to a half-ton of gravel per hour by taking turns, one person shoveling while the other works the bellows.

Some units also have a 12-volt electric conversion kit to allow you the option to either hand-crank in the field or connect to a 12-volt battery for automatic bellows operation.

Various gasoline motor-driven dry concentrating units are available on the market which utilize static electricity and high-frequency vibration to help with gold recovery. Most commonly, there is a high-powered air-fan which pumps air through a discharge hose into the concentrator’s recovery system. The air currents which pass through the recovery system are adjustable so that the proper amount of flow of lighter materials through the recovery system can be obtained-similar to a sluice box in wet-processing. The purpose of the steady airflow is to “float off” the lighter materials through the box. Heavier materials like gold will have too much weight to be swept through the recovery system by the flow of air.

The bottom matting in this type of concentrator is usually made up of a specialized material which creates an electrostatic charge as high velocity air is passed through it from the air discharge hose. Fine pieces of gold, while not magnetic, do tend to be attracted to surfaces which have been electrostatically-charged, similar to the way iron particles are attracted to a magnet. So the bottom matting in these concentrators often attract fine particles gold to itself and tends to hold them there.

Some motorized dry concentrators also use a high-frequency vibrating device to keep the entire recovery system in continuous vibration while in operation. The way to get gold particles to settle quickly down through other lighter materials is to put the materials into a state of suspension. The vibrating device on this concentrator helps fine particles of gold work their way down through lighter materials that are being suspended by air-flows.

Here follows an excellent video demonstration which shows exactly how motorized dry concentrators work:

A motorized dry-washing machine is excellent for the production demands of a one or two-person operation. Under ideal conditions, it is able to process up to about a ton of raw material per hour, which is the equivalent of what a medium-sized wet sluicing operation can produce. This is as much or more than one or two people can usually shovel at production speed when working compacted streambed material. Most motorized dry-washers do their own screening of materials and almost everything else automatically. This leaves the operator free to produce at his or her own comfortable speed.

Total weight of the average motorized dry-washer is about 75 pounds, but the units do break down into separate pieces which can usually be carried around by a single person. So the electrostatic concentrator can be carried to a hot spot if it is worth a few trips to do so. They usually get about 3 hours to the gallon of gasoline.

SETTING UP A DRY-WASHER

There is no fixed formula for setting up the proper air flows and downward pitch on the recovery system of a dry-washer. A lot depends upon the nature of the material that you are processing, how heavy it is, whether or not the material is angular or water-worn and the purity (specific gravity) and size of the gold being recovered. Each of these variables is likely to affect how you must set your recovery system in each different place that it is operated.

The main thing to remember is that the machine needs to separate the gold from the lighter, valueless materials. If you only have a small amount of air-flow running through your dry-washer, then you will need more pitch on the recovery system-and you may need to feed the material slower. Too much air flow can also be a problem. Normally, you would compensate by adjusting to a lesser pitch on the riffle board.

Watch how the material flows over the riffle board. You should see the dirt rise up in an orderly fashion and flow over top of each riffle. It looks an awful lot like water. It is best to keep a steady feed of material going through a dry-washer at all times. The riffles should be filled about half to three-quarters, with a steady flow moving from one riffle to the next. The material in the riffles should have a fluid look to them; they should not be packed solid.

This following very important video sequence demonstrates how to set up and operate a motorized dry-washer, and it shows exactly what you should look for while making flow adjustments to obtain optimum gold recovery:

It is a good idea to shovel lower-grade material into your dry-washer while adjusting for the proper air flows and pitch. Once set, you can shovel in the pay-dirt.

One thing about dry-washing is that because it is generally slower than wet methods, the pay-dirt must have more gold. High-grade areas in the deserts certainly do exist! This is all the more reason to make sure your recovery system is set properly before processing pay-dirt. Chances are that you will not see any gold that might be discharged into the tailing pile through a dry-washer recovery system.

Another thing about setting up a dry-washing production program is that you always set up a dry-washer downwind of where you are working!

Once gold falls into the dead air space within the riffles, it will usually stay there. The air-flows are generally not strong enough to push gold out of there. There is a limit to this, however. Just like a water recovery system, a dry-washer will concentrate the heaviest materials which it processes. After some time, the heavier concentrates may require stronger air flows or a steeper pitch to keep them in suspension. At this point, it is probably time to clean up the recovery system and start all over again. If you are keeping a close eye on your recovery system, you can see when it is time to clean up. The fluidity of the material inside the riffles becomes more concentrated and slows down.

DRY-WASHING AND CLAY-LIKE MATERIALS

Material to be processed must be thoroughly dry to get the best results out of any dry-washing plant. Sometimes you will run into moist clays when out in the dry regions-just like you do in the wet streambed areas. It is also possible to find a pay-layer associated with the clay. Clays make dry-washing procedure more difficult, because they must be thoroughly dried out and broken up before being processed effectively by dry methods.

Sometimes this means the material needs to be set out in the sun to dry for a full day or more before anything further can be done with it. Sometimes it is necessary to dig clay a couple of days ahead of the processing stage. You can alternate spending a day digging and laying out material to dry, and then a day processing dried material. Sometimes, the dried clay can harden into clumps, which then must be broken down into dust and sand before you can recover the gold out of it. When necessary, all of these requirements require more time and energy. But if a good pay-streak is involved, you will find yourself doing whatever is necessary to recover the gold out of it.

It may be necessary to use rock-crushing machinery to break up hardened clay-like material and crush it down on any kind of a production -scale.

The clean-up of concentrates from a dry-washing plant is accomplished best by wet-processing methods. Usually, if you have room-enough to haul around a dry-washing plant in your vehicle, you will also have room for enough water to pan down your final concentrates, too. The following video sequence demonstrates how and when to perform a final clean-up during dry-washing:

If water is not available to you out in the field, the clean-up of your dry concentrates can sometimes be accomplished quite effectively by running them through your dry-washing plant several times. Final cleanup procedures can then be done to separate the gold from the last bit of remaining valueless material.

DESERT PLACER GEOLOGY

The chances of finding a hotspot out in the desert, or in some other dry region, are probably just as good or as your chances of finding a hotspot in the watersheds of the gold-bearing mountainous areas. These chances are pretty good, providing that you are willing to spend the time, study and work that is necessary to implement a good sampling plan.

Probably your best bet is to start off with a “Where to Find Gold” book and study the geological reports which apply to the area(s) of your interest. There has been some small-scale mining activity out in the dry regions. Much of it was lode mining, but some placer activity took place, as well. A good portion of prior activity is recorded information today. It can be of great value to you to know where gold has already been found. It is almost a sure thing that the areas which were once worked for gold at a profit were not entirely worked out. They might be worked again with today’s modern equipment at a profit. Any area which has once proven to pay in gold values is a good generalized area to do some sampling activity to see if additional pay-dirt can be found.

The desert areas were pretty-much left alone by the large-scale mining activities of earlier times because of the accessibility problem. Often, during earlier times, there was not enough water to sustain life, much less to process gold-bearing material.

But desert prospector should not limit him or herself to only the once-proven areas. Most of the desert regions have gone pretty-much untouched by past (effective) sampling activity because of accessibility problems, lack of water, and not having adequate equipment to do the job up until recent years. So the desert prospector has access to a lot of ground, and there are not that many competitors to worry about.

A single large rain or wind storm can change the entire face of the desert in just a few hours. There is very little undergrowth in these areas to prevent a good-sized rain storm from causing an incredible amount of erosion. And so you hear all the old-timers’ stories of finding bonanza-sized gold deposits, marking their position, going out after tools and supplies, and then returning to find the desert entirely changed and the bonanza apparently gone. Undoubtedly, some of these treasure stories are true. After all, many of those old-timers had gold to go along with their stories. Many of them spent the rest of their lives looking for their “lost gold mine.”

All of the placer geology concerning wet areas also applies to desert placer deposits (most which were developed during wet storm events). The same remains true of eluvial deposits-which is the gold that has weathered from a lode and been swept some distance away by the forces of nature. Eluvial deposits in the deserts (called “Bajada placers”) tend to spread out much more widely, and in different directions. This is because they are usually not eroding down the side of a steep mountainous slope. Therefore, they are sometimes a little more difficult to trace back to their original lodes. But it can be done. The answer is to do lots of sampling.

History has shown that one of the best locations to look for gold is where the hills meet the desert and fan out. This is where the water slows down during flood storms and drops gold in the gullies and washes. There also are likely to be more gold traps further up the hillside.

When doing generalized sampling in the desert, concentrate much of your activities in the washed-out areas, where natural erosion has cut through the sediments and created a concentration of heavier materials. Dry-washes, dry streambeds and canyons are good for this. Get an eye for the terrain, looking over the high points and the low points to get an idea of where the water flows during large flood storms. Areas where the greatest amount of erosion has taken place are areas where the highest concentration of gold values might be found. Remember that we are looking at many thousands of years of erosive impacts.

Bedrock will be exposed in some low areas, as in canyons and dry washes. These are ideal places for you to get into the lowest stratum of material-where the largest concentrations of gold values are often found. Large and small canyons have been formed by many years of erosion and are likely spots to find paying quantities of gold.

Caliche is cement-like false bedrock which is commonly found in desert placer areas.(photo USGS)

The desert and dry areas also commonly have a “false bedrock” layer specifically called “caliche.” Sometimes (often), this caliche layer is only a foot or two thick. In some areas, gold is concentrated along the caliche, just like on top of bedrock.

After a storm in the desert, in some places you can find small pockets of gold in the gravel traps, under rocks and under boulders which rest on top of the caliche. Sometimes the gold is pounded directly into the caliche and needs to be removed with a pick or crevice tool. Caliche layers which are close to the surface allow small-scale dry-washing operations to be economically feasible, because of the lesser amount of gravel and material which needs to be shoveled off the gold deposits.

Streambed material can be recognized by the smooth water-worn rocks. Anywhere in gold country, where streambed material is present, is a prime area to be doing some preliminary sampling. Such material indicates that it has been exposed to a substantial amount of running water. This means concentrating activity took place with those same materials. It is possible that the material was once washed out of an ancient river.

However, gravel and material does not need to be water-worn to carry gold in the desert areas. Rough and angular gravel, which has not been greatly affected by water, also sometimes carries gold in volume amounts. Testing is the key.

Sometimes it can be worthwhile to do some sampling in the different layers of desert material when they are present and exposed. Gold concentrations in and between flood layers can happen even more in the desert. This is because of the flash floods which can occur there.

Sometimes substantial gold concentrations can be found just beneath boulders which rest upon bedrock, or up in a layer above bedrock.

When you find a gold deposit in a dry area, whether on bedrock or the caliche, you will want to thoroughly clean the underlying surface upon which the gold is resting. Seldom will you visually see gold in dry placer material-even when there is a lot of gold present. Use a whisk broom or vack machine to clean all of the loose material. Sometimes, it is also productive to break up the surface of the caliche or bedrock with a pick or other crevicing tool.

Occasionally, in dry washes, you can actually see stringers of black sand along the bedrock or caliche-especially directly after a storm. You can sometimes do exceptionally well by following these stringers and digging out the concentrated gravel traps. Do not forget to test the roots from trees and other vegetation in such areas. Vegetation requires a certain amount of mineralization to grow. Roots can grow in and around high-grade gold deposits. I have heard of single roots which have been dug up and produced as much as three ounces of gold!

Some electronic prospectors use their metal detectors to trace concentrations of black sand. Then they follow up by testing the areas which produce the strongest reads from their detectors.

Some desert areas, like Quartzsite, Arizona, also have gold just lying around anywhere-even on top of the ground. Such places are excellent for electronic prospecting and dry-washing. The deserts of Australia are famous for this. I have a number of friends who have been very successful in the Nevada deserts, using metal detectors to recover large numbers of nuggets, some very large, directly off the surface of dry desert ground.

If you find a piece of gold on the surface of a dry placer area, it is likely that there are more pieces of gold in the immediate area. Electronic prospectors call these areas “patches.” Gold generally does not travel alone-unless it was dropped there by mistake.

Sand dunes in the desert are usually not very productive. This is because they mainly consist of lighter-weight sands that were deposited there by the wind. However, sometimes the wind can blow off the lighter-weight sands from a particular location, leaving the heavier materials exposed behind. This is similar to what happens after a big storm at the gold beaches. This is something that should be watched for.

When prospecting around in the dry areas, when you encounter tailing piles from past dry-washing operations, it might be worthwhile to do some raking of the tailings and scan around with a metal detector. Sometimes old tailing piles can be productive enough to run them through a modern dry-washer.