Yes, those are the vats; they're from the cyanide process for extracting gold from ore. The mine hasn't been active since 1941, so I'm not terribly worried about any residues.

The footings of the big stamp mill---at one point it was the biggest mill in California---are a few hundred meters further east, and there are some very broken-down building remnants and miscellaneous timbers, a gigantic open pit, and a lot of random shafts and diggings. There used to be a rusty old washing machine, but I haven't seen it in years and it may have been carried off. The place is easy to find---it's signed on Ogilby Road a few miles north of Interstate 8---and well worth a visit.