Sometimes, where the waters have been arrested in
the hollow of a mountain, they have, in the
same way, dropped an excessive store of gold.
This quality of weight, therefore, is of prime
importance in the history of gold; it
determined the character of its deposits in the first
instance; it enables us now to extract it
easily from its surrounding matter, and it
enables us to detect it in a piece of rock,
where it may not be distinctly visible. There
are two substances which look exceedingly
like gold;—copper and iron pyrites, substances
familiar to most of us. We need never be
puzzled to distinguish them. Gold is a soft
metal, softer than iron, copper, and silver,
although harder than tin or lead. It will
scratch tin or lead; but it will be scratched
with the other metals. That is to say,
you can scratch gold with a common knife.
Now, iron pyrites is harder than steel,
and therefore a knife will fail to scratch it.
Gold and iron pyrites, therefore, need never
be mistaken for each other by any man who
has a piece of steel about him. Copper
pyrites can be scratched with steel. But then
there is another very familiar property of
gold, by which, in this case, it can be
distinguished. Gold is very malleable; beat on
it with a stone, and it will flatten, but not
break; and when it breaks, it shows that it is
torn asunder, by the thready, fibrous nature
of its fracture. Beat with a stone on copper
pyrites, and it immediately begins to crumble.
No acid, by itself, can affect gold; but a mixture
of one part nitric, and four parts muriatic acid,
is called Aqua Regia, because in this mixture
gold does dissolve. A common test for gold, in
commerce, is to put nitric acid over it, which
has no action if the gold be true. There
is, also, a hard smooth stone, called Lydian
stone, or flinty jasper, by the mineralogists,
and touchstone by the jewellers, on which gold
makes a certain mark; and the character of
the streak made on such a stone will indicate
pretty well the purity or value of the gold
that makes it.

We have said that when the gold occurs in
a deep-seated vein, combined with other
minerals, its extraction becomes no longer a
simple process. Let us now point out
generally what the nature of this process is, and
then we shall conclude our brief discussion;
for what else we might say, either lies beyond
our present purpose, or has been made, by the
talking and writing of the last two years,
sufficiently familiar to all listeners or readers.
Mr. Gardner, superintendent of the Royal
Botanic Garden of Ceylon, thus describes the
process of extracting gold out of the mine of
Morro Velho. This mine, when St. Hilaire
visited it, was considered as exhausted; it is
now one of the richest in Brazil. Thus
Mr. Gardner writes of it:—

"The ore is first removed from its bed by
blasting, and is afterwards broken, by female
slaves, into small pieces; after which it is
conveyed to the stamping-machine, to be
reduced to powder. A small stream of water,
constantly made to run through them, carries
away the pulverised matter to what is called
the Strakes—a wooden platform, slightly
inclined, and divided into a number of very
shallow compartments, of fourteen inches in
width, the length being about twenty-six
feet. The floor of each of these compartments
is covered with pieces of tanned hide,
about three feet long, and sixteen inches
wide, which have the hair on. The particles
of gold are deposited among the hairs, while
the earthy matter, being lighter, is washed
away. The greater part of the gold dust is
collected on the three upper, or head skins,
which are changed every four hours, while
the lower skins are changed every six or
eight hours, according to the richness of the
ore. The sand which is washed from the
head skins is collected together, and amalgamated
with quicksilver, in barrels; while
that from the lower skins is conveyed to the
washing-house, and concentrated over strakes
of similar construction to those of the stamping
mill, till it be rich enough to be amalgamated
with that from the head-skins. The
barrels into which this rich sand is put,
together with the quicksilver, are turned by
water; and the process of amalgamation is
generally completed in the course ot forty
eight hours. When taken out, the amalgam
is separated from the sand by washing. It
is then pressed on chamois skins, and the
quicksilver is separated from the gold by
sublimation."

Let us explain those latter processes in
more detail. If you dip a gold ring or a
sovereign into quicksilver, it will be silvered
by it, and the silvering will not come off.
This union of theirs is called an amalgam.
On a ring or sovereign it is mere silvering;
but when the gold is in a state of powder,
and the amalgamation takes place on a
complete scale, it forms a white doughy mass, in
which there is included much loose
quicksilver. This doughy mass is presently washed
clear of all impurities, and is then squeezed
in skins or cloths, through the pores of which
loose quicksilver is forced, and saved for future
operations. The rest of the quicksilver is
burnt out. Under a moderately strong heat,
quicksilver evaporates, or—to speak more
scientifically—sublimes; and gold does not.
The amalgam, therefore, being subjected to
heat, the quicksilver escapes by sublimation,
leaving the gold pure. The quicksilver escapes
by sublimation; but its owner does not wish it
quite to escape out of his premises, because it
is an expensive article. Chambers are therefore
made over the ovens, in which the
mercury may once again condense, and whence
it may be collected again afterwards. But,
with all precaution, a considerable waste
always takes place. Other processes are
also in use for the separation of gold from
its various alloys. We have described that
which is of most universal application.