Is there any gold in that river sand?

In gold prospecting, as in life, nothing is black and white. In fact, it’s frequently black and gold. This is especially true when it comes to gold prospecting in river sand. You may have noticed areas of black sand amongst the otherwise pale river sands. The black sand consists of iron, hematite, sheelite, chromite, iron pyrite and other heavy metals. This black sand is much heavier than the lighter colored sand and this is why it’s is very significant for gold prospectors.
Black sand weighs about 5-11 times more than the same volume of water1 whereas gold weighs around 19 times the same volume of water. How does this help you? Gold follows a largely predictable path down the river from its source. Because of its weight, gold nuggets require fast-moving powerful rivers or flood conditions to transport the gold downstream. As the river slows, at the exit to canyons or behind large rock outcrops, the heavy gold sinks to the riverbed. The next flood will pick it up again and the journey down the river continues. During this rough and tumble journey the gold nuggets may be pounded into increasingly smaller pieces. Eventually, the gold nuggets are transformed into fine flakes or powder.

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Image courtesy of: http://mygoldpanning.com/rivergold.html
Thanks to the similarly heavy nature of the gold flakes and the black sand, they tend to be deposited in the same areas. Therefore, if you are in a known gold-bearing river and you see black sand you will probably find gold there also. You could say, ‘black is the new gold’.

How do I get that gold?

Panning is the classic method for working in river sands. The tricky part is separating the gold from the black sand, and the finer the gold the greater the difficulty. You need patience and good technique.
Begin by classifying your material through a sieve—that is separating the larger gravel and small stones from the fine sand. A number 8 screen has about 32 holes per square inch and is a good size to prepare your material for panning. Don’t forget to check through your pile of stones for nuggets. Now to work with the sand that is left.

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Essentially, panning is replicating the action of the river to separate the black sand particles from the heavier gold flakes. The gentle swirling action of the water in the pan will move the lighter sand out over the lower edge of the pan leaving the heavier gold and some black sand at the bottom. It will require some practice and experimentation to find the right speed and angle but the movement can be very calming and relaxing in itself. Every so often, stop and check the material left in the pan. You may need tweezers or a plastic bottle with a nozzle to suck up the fine gold.
Don’t be fooled—all that glitters is not gold. Often you will find shiny, flakes that in certain light appear golden. These flakes are probably mica. If they change color and are soft or you can break them with your tweezers they are not gold.

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Images courtesy of: http://www.goldgold.com/tag/gold-panning-2
1 http://hookedongold.com/black_sand_what_is_it.htm