One problem/danger thst is if often overlooked when HF is used
for quartz removal is that the quartz mostly ends up in the form
of a very, very toxic gas. Not only is there the short term
toxicity, but long term the effect on the lungs is very serious.
HF liquid is a “weak” acid as far as the effects on most metals
is concerned. It is, however, very bad on skin and eyes. Much
more dangerous to skin and tissue than “strong” acids are.
In these days it is more difficult to get chemicals than it once
was. If you know someone at a local college, you should be able
to get a small quantity from there. Chemical supply houses do not
sell to anyone but listed companies. It will be necessay to
establish yourself with them.
Unless the concentration of gold is rather high in the quartz,
it would be difficult to not spend more for the chemicals, labor,
etc. than the qold is worth. The rate of solution is slow without
boiling the liquid and what do you boil it in? All ceramics and
glass are out. In lab sized experiments, it is usually boiled in
a platinum dish which works very well. What quantity of quartz do
you have to treat?