The panning was done both as an experiment to see if I could
recover something useful, and to try to get an idea how much
gold was in there as a percentage of weight. The results of
this seems to confirm that I did NOT get back from the refiners
what was sent. (Hoover & Strong was one of the ones used)
Panning like that will not provide an accurate sample, since it
will select for the larger, higher karat pieces, while allowing
lower karat smaller pieces of metal to stay with the rubber wheel
dust. When really panning for gold, your looking for an almost
pure, highly dense metal, and seperating it from nonmetallic
sands, a much greater difference in densities. Even then,
magnetite sands stay largely with the gold, and they are still
farther away than your varied gold dusts.
Also, remember that when you send scrap for refining, there is
always some loss. This is NOT due to dishonesty by the refiners,
but to the simple fact that refining is not perfect. Some gold
simply evaporates during melting, some remains in solutions, some
remains in slag, filters, crucibles, etc. Expecting to be paid
for these losses is unrealistic. If the refiners had to operate
at perfect efficiency, with no losses, the resulting higher costs
of operation would more than offset the regained metal. What
they are returning to you is generally the best available
compromise between high yield and low cost.
If you are unsure of this, the way to test it is not to try and
pan your gold. That simply cannot produce an accurate sample.
Instead, wash it in detergent, remove iron with a magnet, burn in
an open iron frypan to remove organics (just get it hot enough
over the stove to burn off the wax, is sufficient, and then pack
it all into a graphite crucible with plenty of the appropriate
fluxes (A mix of borax, boric acid, a little ammonium chloride,
and a bit of charcoal powder is what I’ve used.), put it in a
furnace, and melt all your scrap, remaining rubber, abrasives,
and all, down to an ingot. This simply requires long enough
(several hours) in the furnace (not a torch melting job) to let
all the gold settle down, even from tiny pieces. Temp needs to be
high enough to completely melt the highest melting gold you use
Pour the resulting melt into a thick ingot mold. Retain the
crucible for the next time, so losses in your own crucible don’t
accumulate beyond a certain point. One thing you will find when
doing this is that somehow, you’ve always got less weight in
that ingot than you expected to have. But an examination of the
remaining flux in the crucible will show that most of the metal
is actually in the ingot. It’s not your error, it’s simply the
nature of scrap filings and such to often contain less metal than
we think or hope we’ve got. It’s what’s confusing your estimates
with the refiners as well.
With the ingot, now drill several holes all the way through at
various points, both in the center and near the edges (Ingots do
NOT have absolutely uniform gold content everywhere, since
progressive solidification concentrates certain metals in the
center and others at the edges.) Collect the drillings. Wash
off any oils. These drillings are now considered a uniform
sample of the metal in the ingot. You need a gram or so, which
is now sent to an assayer for an independent assay.
NOW you have an idea of what you’ve got. Also, when you now
send that ingot in for refining, those drill holes will serve as
notice to the refiner that you’re not working blind, and know
what to expect in return. Plus, because you’ve done the messy
melting part yourself, you’ve eliminated much of the
unpredictable loss, and the refiner will pay you for what you
expect, not for some lower amount when you thought you were
sending more.
Peter Rowe