There have been many questions about how to get gold out of black sand. So I thought I would post a method I use to clean up my 8" Dredge. I clean up the top of my sluice box every day and the rest of the sluice box when it is needed. One problem I see with many new miners is they clean up too often, which takes away from the time they could be dredging and finding more gold. However, 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 setup for the sluice is so you have about one-quarter inch of carpet between the gravel of the middle riffle of the channel 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). I put in a vial any gold found in the concentrates that were too large to fit through the 20 mesh screen. 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 to the top to catch fine gold. I then start the engine on an idle dredge, so the water runs down the shovel sluice. I adjust the machine so that the water flow is swift enough to wash out light sand and still save all of the black sand and gold. The output 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 run. I then empty the shovel sluice into a 5-gallon bucket. I then have <20 extreme mesh concentrate.
I use a panning wheel and a micro sluice to do the final clean-up. 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 clean-up. Personally, in general clean-up, I like to stay away from the use of mercury, as there is a faster way without it. I also want to avoid nitric acid because it's usually not needed either. However, there are times when mercury and nitric acid can help speed things up. Usually, though, I can do the final clean-up without them.
- Here's one quick procedure to do the final clean-up;
Dry out the gold by pouring it into a metal pan and heating it over a stove outside. Please don't get it so hot that any pieces of lead still with the gold will melt. Instead, heat it 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. Mercury attaches itself to gold in different amounts. Often it's there, but you can't see it. When heating the gold to a certain temperature, the mercury vaporizes. These vapors are very dangerous. So it is good practice to heat your gold outside and downwind of you, even when heating it just enough to dry it out. Also, You should use the pan you use for heating gold during clean-up only to clean up, not for cooking. I use a portable hot plate for this.
- 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.
- Now, You can use a magnet to extract most of the remaining black sands for your gold. I use a super magnet, but I used the Keene Gold Magnet. The Super Magnet is just larger.
- 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.
- Put your gold back in the metal pan, take it outside, and heat it, hotter this time, to vaporize any other mercury for the gold. This will bring your gold back to the raw, rich beauty we love.
- Now, you can put it in a bottle. If you want to sell it, keep it dry, but if it is for a 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.