Mining for gold with a dry washer
Dry washing, or, the recovery of gold from gravel by dry seperation, is a very popular method in southern california. A dry washer can also be called a dry jig. A dry washer processes dry gold-bearing gravel by intermittent pulsations of air, wich seperates the heavy minerals from the light ones. The light minerals pass through the machine to a waste pile; heavy minerals such as gold and black sand stay behind in the riffles.
A dry washer consists of a screened hopper at the top, with a feed box and a cloth bottomed, inclined riffled tray. Bellows are below the tray. The bellows push air up through the cloth lined tray thus seperating the light minerals from the heavy. Gravel fed through the hopper descends to the riffles by the machines agitation.
Some people pour a little mercury behind the riffles to catch flour gold as the machine can loose some smaller flakes with the lighter material.In one day a dry washer can process two cubic yards of gravel. When the riffles are full of concentrates, the tray is removed and the material panned.
The electrostatic dry washer is an advanced machine wich seperates the light material from heavy minerals by static electricity. It is an expensive machine but its recovery of flower gold is 85% wich is excellent. Compared to a normal machine that catches an average of 20% of smaller gold.
For a dry washer to work the gravel must be dry to the point of dusty. damp gravel will not pass through the riffles as well and gold sticks to damp gravel. In many dry placer drift mines, the machine can be operated underground.
As for the gravels to be worked, the best places are bedrock, crevices, ledges, cracks and natural riffles. Stay with the lowest, deepest parts of washes because the gold was concentrated by erosion. The dumps below underground dry placer workings are great spots. Remember, the top of the dump came from the bottom of the shaft. Good luck!
Gold found on surface in northern california
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