beekbuster,
hydrofluoric Acid (a solution of HF in water) as you've indicated is Very Bad Stuff! There is a limit of human exposure with this acid, likely you can find it on an MSDS sheet (Material Safety Data Sheet or they may have abbreviated it to MSD. There are three exposure limits to this material, after the first exposure the unlucky person becomes very sick including removing everything from their stomach they've eaten in the last three months. After the victim gets over that they put a medical alert bracelet on their wrist that lets ER people know how to treat the victim should they have a second exposure. At the time of the second exposure the victim will be unconscious so they will not be able to explain to the ER folks what happened. After the third exposure to HF they will place the victims body into a heavy plastic bag because the victim has died. Why? HF builds up in the human body, similar to lead, once the maximum quantity has been stored up it keeps the victim from the fourth exposure.
I could easily be incorrect but I thought Nitric Acid could be used for etching host rock away from Gold! It depends on the strength of the acid to work, more or less true for all acids, and the host rock material.
Regardless of the acid suit up, that would be a rubber apron with gloves above the elbows(acid specific materials need to be used: neoprene, natural rubber, etc.), a breathing mask of the proper type and and eye protection (minimum glasses but more likely a hood or mask). I know You care which is why you posted your question and it is wise of you to care as acids will take skin, eyes, etc. up to and including a persons life IF they do not take proper safety precautions.
Also, TEST a tiny piece of the host rock in a very small quantity of the acid. If there is a VIOLENT REACTION you want only small quantities of each to be involved. Violent reactions can be from heavy bubbling to an explosion like reaction, either of which can throw the acid all over everything in the general area of the Accident.
Work carefully with these materials, do your research. The results of careful etching work are absolutely beautiful!...............63bkpkr