How to get the Black Sand out of your Gold.
Susquehanna River Chapter of GPAA
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How to get gold out of black sand without mercury.
Here's how to do it.
By Tom Ashworth
There have been many questions about how to get gold out of black sand. I thought I would post a method that I use on cleaning up on my 6" Dredge. I clean up the top of my sluice box everyday and the rest of the sluice box when it is needed. One problem I see with a lot of new miners is they clean up too often and this takes away from the time the could be dredging and finding more gold. If you have the sluice on your dredge set up so that the gravel is not getting too full between the rifles and not running so fast that it sweeps the rifles, then once a day clean up is all you should need on most store bought dredges. The perfect set up for the sluice is so you have about one quarter inch of carpet showing between the gravel of the middle riffle of the sluice and the one below it. Now dredge all day.
After dredging all day I empty my dredge into a large wash tub. I then screen those concentrates using a 20 mesh screen into a 5 gallon bucket. I then pan the concentrates that did not go through the 20 mesh screen while down at the river (looking for nuggets of course). Any gold found in the concentrates that were to large to fit through the 20 mesh screen, I put in a vial. I then put a shovel sluice (a Keene or Le Trap sluice works well) inside the dredge sluice so that the shovel sluice is close to the header box or jet flare (Note: This only works on 5" and larger dredges). I use a modified Keene A-52 sluice. It has some NoTrax matting glued in the top to catch fine gold. I then start the engine on the dredge at idle so the water runs down the shovel sluice. I adjust the engine so that the water flow is swift enough to wash out light sand and still save all of the black sand and gold. The out put of the shovel sluice goes back into the dredge sluice and there are still several riffles in the dredge sluice that will catch any flour gold that happens to escape (this will remain until the next time I dredge). I then scoop the concentrates that I screened into the shovel sluice. When all concentrates are ran. I then empty the shovel sluice into a 5 gallon bucket. I then have <20 mesh extreme concentrate.
To do the final cleanup I use a panning wheel and a micro sluice. You can also pan down to get to the last of the impurities. These impurities usually consist of a small amount of black sand, a few iron rocks, and pieces of lead.
There are many ways to go about doing this final cleanup. Personally, in general cleanup I like to stay away from the use of mercury, as there is a faster way without it. I also like to stay away from the use of nitric acid because its usually not needed either. There are times when the use of mercury and nitric acid can help speed thing up. Usually though, I can do the final cleanup without them.
Here's one quick procedure to do the final cleanup;
(1) Dry out the gold by pouring it into a metal pan and heating it over a stove outside. Don't get it so hot that any pieces of lead which are still with the gold will melt. Heat it up just hot enough to dry it out. It is a good idea to stay upwind anytime you put gold in a pan and heat it up. Mercury attaches itself to gold in different amounts. Often it's there but you can't see it. When heating the gold to certain temperature, the mercury vaporizes off. These vapors are very dangerous. So it is good practice to heat your gold outside and downwind of you, even when heating it up just enough to dry it out. Also, the pan you use for heating up gold during cleanup should be used only to cleanup, not for cooking. I use a portable hot plate for this.
(2) Once the gold is dry, bring it inside, out of the wind, and pour it onto a piece of clean paper. You can now pick out the larger impurities from the gold with tweezers.
(3) Now a magnet can be used to extract most of the remaining black sands for you gold. I use a super magnet, but I used to use the Keene Gold Magnet. The Super Magnet is just larger.
(4) By lightly blowing over the gold, you can finish extracting the rest of the impurities. If you can locate a very fine screen you can use it to separate the smaller pieces of gold and impurities from the larger ones just after drying it out. This speeds the process up a bit.
(5) Put your gold back in the metal pan, take it outside and heat it up, hotter this time, in order to vaporize any further mercury for the gold. This will bring your gold back to the basic deep rich beauty which we love.
(6) Now you can put it in a bottle. If you want to sell it keep it dry, but if it is for show put water in the bottle to keep it beautiful. The water will also prevent the glass vial from breaking due to the weight of the gold.
HOW TO USE MERCURY TO RECOVER GOLD
by Tom Ashworth
LEGAL NOTICE
Tom Ashworth (the author) shall not be liable for incidental or consequential damages in connection with or arising out of the furnishing or use of this material. I have no control over how you do these procedures. This procedure works for me and if something gets messed up it is your problem, not mine!
WARNING
The processes contained herein require the use of high heat, mercury and very dangerous acids, and must be performed in a well ventilated area. Always use mercury, sulfuric acid and nitric acid in a well ventilated area. DO NOT breathe the fumes.
Mercury begins to vaporize at room temperature and its fumes can be deadly.
Fumes from many ores are deadly when heated.
Nitric acid can be absorbed through the skin causing nitric acid poisoning. WEAR RUBBER ACID GLOVES. Always add acid to water, NEVER ADD WATER TO ACID!
Mercury and nitric acid can kill if swallowed.
Nitric acid can ruin your clothes and shoes.
Always wear rubber gloves, plastic safety glasses and a plastic or rubber apron.
IF YOU DO NOT UNDERSTAND ALL OF THE ABOVE WARNINGS, DO NOT GO ANY FURTHER!
EQUIPMENT USED
Large copper gold pan
Rubber spatula
Tweezers
Oral syringe or large veterinarian's syringe
Virgin cotton balls
Pyrex Beaker
INGREDIENTS USED
Mercury
Nitric acid
Distilled water (With no chlorine)
Mercury
NOTES
Any clean water without chlorine. Chlorine mixed with nitric acid can dissolve gold. Gold must be clean in order for mercury to attach itself. Sometimes placer gold will be covered with a thin film of oil, which will prevent the gold from being amalgamated unless the oil is cleaned off first. CAUTIONS: Working with nitric acid, can be very dangerous. Be extra careful to avoid spilling it on yourself or splashing it in your eyes. DO NOT breathe its fumes! When a solution of nitric acid is poured onto a dirty set of concentrates, the effect will be a bubbly reaction. Allow the concentrates to bathe until all such visible reaction has stopped.
PROCEDURE
1. Soak the concentrates in a 10:1 solution of nitric acid, which means 10 parts of water to 1 part of nitric acid. use a Pyrex beaker. This is to clean the gold. You can do a better job of this if you put the concentrates and the 10:1 solution in a rock tumbler with a plastic or rubber barrel (no metal, acid will corrode the metal).
2. Rinse the concentrates with fresh water so that the acid is diluted and washed away. Once this is done, the concentrates are properly set up for amalgamation.
3. Take a clean, large, copper gold pan and coat thoroughly with mercury, using a pad of folded cloth. Deposit the concentrates in the pan, add some fresh water and swirl and agitate until all visible gold has been taken in by the mercury. If you want to check for platinum, if you suspect it may be present, wash the black sands into a separate pan which can be checked later.
4. Using a rubber spatula, scrape the gold bearing mercury from the copper gold pan into a Pyrex beaker.
5. Wet a ball of virgin cotton and squeeze out the excess water. Place it into the bottom of an oral or veterinarian syringe and pour in the amalgam ball. Replace the plunger and holding the end of the syringe over a container, press the plunger to extract the excess mercury. If the container is filled with water, the mercury will be prevented from splashing or bouncing out as it drops into the container if you hold the end of the needle under the surface of the water.
6. Remove the plunger from the syringe and extract the cotton containing the amalgam, using tweezers. Put the amalgam ball into a Pyrex beaker and set it in a safe place, downwind of any populated area within the vicinity.
7. Mix and pour in a solution of nitric acid and allow it to bubble until there is no visible reaction. BE CAREFUL NOT TO BREATHE THE FUMES GIVEN OFF BY THE CHEMICAL REACTION!
8. Pour off the acid solution into another glass jar or a beaker; so that, the mercury in solution can be recovered later (see how to do below).
9. If all of the mercury has not been dissolved from step 7, with the gold back in its natural flake and powder form, pour fresh water into the jar and use an old screwdriver to poke it around and break it up. Pour out the water and pour in another solution of nitric acid. Sometimes it is necessary to poke at the gold just a bit to break it up while it's being worked on by the acid. An old screwdriver works well for this.
10. When the reaction stops, flush with fresh water. If the gold is still not back in its natural form, repeat the above steps. When dealing with small amounts of amalgam, usually the gold will be thoroughly cleaned of it after step 7. Sometimes when working with larger amounts of amalgam, it is necessary to do the steps a few times as described above, or to use a stronger acid solution. NOTE: if you have a large amount of concentrates, you may wish to ignore steps 3 and 4 and place the concentrates and an estimation of the correct amount of mercury into a rock tumbler and allow it to turn for several hours. Some large scale operations employ the use of portable cement mixers. If a new cement mixer is used, run it first with a full load of sharp sand and gravel for 10 to 12 hours to scour out any paint that may be present, as it will contaminate the mercury.
RECOVERING THE MERCURY
FROM THE NITRIC ACID SOLUTION
To recover the mercury in solution (see step 8), simply drop some aluminum foil into the acid solution. A chemical reaction takes place and the acid solution will drop the mercury to attack the aluminum. This causes the mercury to revert to its natural liquid metal form at the bottom of the jar. Then rinse out the acid solution and you will be left with most of your original mercury.
CLEANING MERCURY
After mercury has been used a number of times in the process of amalgamation, it becomes dirty and tends to break down into smaller, separate balls instead of it all coming together into a single mass. To clean dirty mercury, you simply soak it in a nitric acid solution of 30:1 part of acid. This will clean the impurities out and allow it to amalgamate properly again. Mercury can be used over and over to amalgamate and cleaned when necessary in this way.
