I once took a sample of fines from my claim in to a jeweler to see what he would give for my placer gold.
He brought out an 8" tile set in a wooden frame, from beneath the counter, took a sample from my vial with a small knife and dropped it forcefully on the center of the tile... it scattered.
He scraped it together in a pile, looked at it with a loupe, then dripped a bit of nitric acid on it, looked again and made me an offer. I refused, and he did a quick job of scraping my little sample pile up and putting it back in the vial.
I'm sure he did that with everyone who brought in a sample of fines.
Probably made a few bucks a day off people, that way.
I never went back.