A_Historic_Site
Gold_mining_today marshall SutterSFARM
blank discovery the 49ers
historic images posters how california changed

The popular images of gold miners from the Gold Rush, either panning for gold nuggets in a mountain stream or digging into thick veins of gold with pick-axes, bear almost no resemblance to the way gold is mined today.

Most rich veins of gold, where gold could be separated in solid chunks from the surrounding ore, have been exhausted. Today, gold mining is as much about chemistry of solvents than it is about the rough physics of a shovel and pick axe. This is because today gold is primarily found in very low concentrations – less than 10 grams per ton. The only way to extract gold, found in such small particles and at low weights, is to excavate large amounts of ore from mines, by blasting to create large open-pit mines. The excavated ore is pulverized into fine powder to free the gold from the surrounding ore.

It is then treated with water, to create a muddy mix called a slurry. At this point, the ore is treated with a liquid solvent that will dissolve the gold.