So, 1. I know this thread is old and 2. Someone else may have already commented and I just didn't see it, but..... dimethyl mercury is a neurotoxin - one of the most potent ones currently known to man due to its ability to cross the blood-brain barrier, which is why Wetterhahn died. In fact, Dimethyl Mercury is so dangerous, that even back in '98, when Wetterhahn died, scientists did not generally use this form of mercury, they used standard, nontoxic mercury salts, which is easier for the human body to expel should it come into contact with you. Since the incident with Wetterhahn, Dimethyl Mercury has been made illegal, and you can't get it to use, especially for home projects, even if you wanted to. Whereas the mercury being discussed above is a liquid metal (Symbol Hg on the periodic table), is also known as "quicksilver" because of its fluidity, and is commonly used to capture fine gold flakes and particles. Mercury is also the only common metal that is a liquid at room temperature. Also, according to the CDC, if a small amount of mercury is ingested, most of it will pass through your body and not hurt you. If it is handled for any length of time, a small amount may enter your body through your skin, but again, will not be an amount large enough to hurt you. Mercury, when it is left out in the open, can vaporize. This fills the air with invisible, odorless, tiny mercury atoms which are oil and fat soluble - making it harder for your body to get rid of. If mercury vapor is inhaled, it becomes a poisonous, odorless nerve gas which it is easily absorbed by the body. When you breath it in, it goes straight to your lungs and from there into the blood and the brain. The nerve poison can cause sleep disorders, agitation, and paralysis.
But - as long as you are not inhaling mercury fumes from heated or vaporized mercury, you are safe to use it for extricating your gold from the contaminants. This is why the other member made sure to stress to use it outside, not to breathe in the fumes, and to wear gloves, etc. Same with the lye, although I can tell you from personal experience that the fumes from Lye mixed with water is NOT odorless.... that stuff will let you know it is there. It burns and makes you cough! Anyway.... Just thought I would throw my two cents in, even if it is 14yrs after the thread was written LOL!!!
Why would you choose to dissolve the valuable metal over removing the worthless bentonite (mica)? Even a couple of grams of gold is worth something whereas mica is not worth anything - unless you have ties to cosmetic companies and can sell it in bulk, since it is used in a lot of makeup.