The derivation of the equation is a little hairy so I’ll just
present it in it’s final form. Assuming the specific gravity of
pure gold is = 19.3 and Quartz = 2.66, the equation you need is:
% Gold = 116 - 308.5/S.G.of specimen For example, if your
specimen has a S.G. of say 12.3, the % gold in it will be: % gold
= 116 - 308.5/12.3 or 116 - 25.08 or 90.92% (and the Quartz, of
course is, 9.08%) Happy New Year and Happy Calculating…Bob
Williams
Woops! How are you going to compute the ratio of quartz to gold
if you don’t know the purity of the gold? Gold in nature is
never pure; nature alloys it with a wide panoply of other
metallic elements. A typical purity would be .875 , but the
range is extremely variable even within the same mine. On the
other hand, if you were to remove the quartz from the specimen
by dissolution in hydrofluoric acid, you would then be able to
compute the purity of the gold by determining the specific
gravity of the specimen. Unfortunatly, the latter solution works
only when the natural alloys do not include those elements which
approach gold in specific gravity. Almost every occurence of
gold in America has been documented and dissected and a
reasonable average purity of most occurences would be recorded
in USGS and other monographs. Thus, with a certain amount of
research, you could probably determine the approximate gold
content of the specimen. I once had a miner bring a specimen
into my shop which weighed approximately forty pounds and seemed
to be about fifty per-cent free gold. He wanted ten thousand
dollars for it, but this kind of specimen is so rare that
bullion content wouldn’t be a prime consideration. Good luck!
Ron at Mills Gem , Los Osos, CA. P.S. Don’t even think about
screwing around with hydrofluoric acid unless you are prepared
to meet your maker…it is the nastiest of the nasties ! R.