Besides silver it separates out gold.
The lighthouses used a pool of mercury to float the lamp assembly on. This was rotated by clock work using weights that hung in the tower These lamps weighed a lot and mercury was the best way to reduce friction. A lot is what you get when I can’t pull up a weight for one of the lamps searching the web.
The Kilauea Point Lighthouse on Kauai, Hawaii was built in 1913 with a four-and-a-half ton lamp suspended on a mercury float.
Thanks, I thought they weighed tons, but didn’t want to say that without an example. By the way that was the weight of the lens and not the whole assembly, so the lamp weighed more.
Right between the Sun and Venus.
The bulk of the mercury from New Almaden was used in gold and silver mining, and was critical to the gold rush. The ore in California and in the Virginia City, Nevada area was quartz veined (usually very finely) with native silver and gold. To extract the metals, the ore was first pulverized by stamp mills, which ran 24/7, shaking the earth and disturbing the sleep of all in the vicinity. Then liquid mercury was used to dissolve the metals from the resulting powder. The resulting amalgam of silver, gold and mercury was then heated to drive off the mercury. Recovery of the mercury vapor ranged from ineffective to nonexistent. You can read a bit about this process in Mark Twain’s Roughing It, among other places.
Another use for mercury was in jewelry. “Gold” in jewelry is not pure (that wouldn’t keep its shape), but an alloy; “white gold” used to include mercury (it doesn’t any more), while “red gold” is rich in copper.
I haven’t heard of any widespread use of mercury in white gold in the past. Mercury is used as an amalgam in silver fillings, but where exactly was it purposefully used in white gold?
Ok, now I don’t feel so bad telling you to look for it about 7 degrees above the horizon in the evening sky right after the sun sets. 
I"m looking Askance at post #24