- Not all good is retrieved with mercury. As a matter of fact, I think
mercury “leaching” is illegal and rarely done anymore. It is an
interesting process, though, whereby gold is recovered by pouring
mercury over it, often in river beds. The gold “melts” into the mercury
which then carries it further downhill. Then the gold-bearing mix is
heated to evaporate the mercury, leaving the gold behind.
G’day; here’s another penn’orth:- In some of the creeks of New Zealand,
and in some ancient sand dunes on the West Coast of the South Island the
gold is so fine that it is hard to see. (there’s a very old ballad
called, “There’s Gold, Bright Fine Gold In The Mataura”)The miners crushed
the consolidated sandy rock and washed it down a wooden slope with bits of
wood nailed across it, (called a riffle box) which caught the larger bits.
Next came a piece of sheepskin fleece (Jason’s Golden Fleece?) which
caught the finer stuff, though in the later years carpet seemed to work
better . Finally came copper sheets, coated with plenty of mercury, and
this caught the very finest gold, amalgamating with it. The amalgam was
scraped off as a thick yellowish paste and placed in a retort made of iron
pipe, and the main vessel was heated in a fire (usually the camp fire).
The mercury was thus recovered, and the spongy gold was melted and poured
into a bucket of water, then they waited for the itinerant gold buyer to
come around to the goldfield.
The very early prospectors, with the very finest gold in their pan used to
amalgamate it with mercury. Then they’d get the biggest potato they could
find, hollow it out and leave a sort of gallery. They would then put the
putty-like gold amalgam on their shovel, put the spud over it and heat it
on the fire. The mercury distilled off, collecting in the gallery, from
whence it could be poured out to be reused, and the gold sponge would
remain on the shovel. An early example of Kiwi ingenuity, and I’ve
actually seen it done.
I hope not too many ate the well cooked spud afterwards.
I really can’t imagine the prospectors - who were all extremely poor -
wasting expensive mercury by pouring it in the creek in the hope they’d
get it back further down.
These days they treat the crushings with dilute sodium cyanide solution
and bubble air through the liquid, which dissolves the gold then plate out
the gold electrically, which leaves a far more pure gold than the mercury
A lot cheaper too.
/ /__| \ @John_Burgess2
At sunny Nelson NZ (in winter)