LOSS OF THE PRECIOUS METALS.
The divisibility of quicksilver, and also of silver and gold, as shown
by the milling operations conducted in Nevada, is incomprehensibly
great, and would seem to be almost unlimited; particularly in the case
of the metal first named. A globule of quicksilver may be divided until
no longer visible to the naked eye, and, indeed, until scarcely visible
under a microscope, and yet even the most minute subdivision shall be
found to contain both gold and silver. How infinitesimally small, then,
must be the particles of silver and gold contained in one of these
almost invisible and immeasurable globules of mercury!
In regard to the remarkable divisibility of the precious metals, the
following instance may be given in illustration: The superintendent of a
water mill on the Carson River, when working for a considerable length
of time an ore in which gold largely predominated, used every precaution
to guard against loss. In addition to the usual settling-tanks, he
caused to be dug in the ground a number of large pits, into which the
waste water flowed after leaving the tanks.
After leaving these pits, the water passed off in a small flume, and to
the eye appeared as clear as the water of the purest mountain stream.
For the sake of experiment, the superintendent coated a copper bowl with
quicksilver, and placed it in such a position that the water from the
flume should fall into it. He also placed in the flume, below the bowl,
some copper riffles, properly coated with quicksilver. Although the
water passing through the flume appeared to be perfectly clear, yet at
the end of three months the bowl and riffles were cleaned up and over
$100 in amalgam was obtained.
This mill is driven by water taken from the Carson River, and carried
for a considerable distance through a large wooden flume. At one time it
became necessary to shut off the water, for the purpose of repairing
this flume. In making the repairs it was found that in many places that
the heads of the nails driven into the bottom of the flume were thickly
coated with amalgam. Within a distance of about three rods along the
flume, the workmen engaged in making repairs collected over an ounce of
amalgam. The water flowing through the flume was taken from the river,
below a number of large mills, and, though far from being clear, would
never have been suspected to contain floating quicksilver in such
quantity as to form collections of amalgam on the heads of iron nails.
In order that quicksilver may amalgamate with iron, the iron must be
scratched or polished while immersed in the quicksilver; it will
therefore be seen that much amalgam must have passed by before the
accidental occurrence of the conditions under which the collection of
amalgam on the heads of the nails could begin. As a beginning, a passing
pebble must have pricked through a globule of quicksilver just at the
moment when it was rolling over the head of a nail. By a succession of
these accidental collisions the head was finally covered with
quicksilver, and the collection of amalgam then went on rapidly.
As further evidence that quicksilver in considerable quantities floats
in the water of flumes and streams, below reduction-works, in a state of
invisible division, and yet carries with it the precious metals, I may
give an additional instance. At a mill on the Carson River one of the
workmen required a piece of copper. Remembering to have seen some old
sheets of that metal lying near the waste-gate of the flume, through
which water was brought to the wheel of the mill, he went to the spot
and hauled them out of a puddle in which they were lying. Much to his
surprise he found the sheets heavily coated with amalgam and so eaten up
by quicksilver that they were as thin as writing paper. The water
pouring out through the waste-gate had a fall of about fifteen feet. It
did not fall directly upon the copper plates, but in such a way as to
keep them constantly splashed and wet. The plates had lain where they
were found four or five years. Over a pound of amalgam was scraped off
them. It would seem that in these striking instances of the unsuspected
floating away of the precious metals there is for millmen food for
reflection, and for inventors a field of profit and distinction.
Just what becomes of all the quicksilver used in the reduction-works of
Nevada is a question which has never yet been fully and satisfactorily
answered. Much floats away with the water flowing from the mills; but it
cannot be that the whole of the immense quantities used is lost in that
way. Quicksilver in great quantities is constantly being taken into the
State, and not an ounce is ever returned. When it has been used in the
amalgamation of a batch of ore, it is taken to the amalgamating-pans,
and is used over and over again until it has disappeared. Whether it may
float away with the water used in amalgamating, or is lost by
evaporation while in the hot-bath of the steam-heated pans, there must
be a vast amount of the metal collecting somewhere, as it is a metal not
easily destroyed. In case it is lost by evaporation it must condense and
fall to the ground somewhere near the works in which it is used, and if
it floats away in the water it must eventually find a resting place on
the bottom of the stream in which it is carried away.
It is an axiom among millmen that “wherever quicksilver is lost, silver
is lost;” therefore there must be a large amount of silver lost, as we
shall presently see. The amount of quicksilver used by mills working the
Comstock ores alone averages 800 flasks, of 76½ pounds each; or 61,200
pounds per month. This in one year would amount to 734,400 pounds of
quicksilver that go somewhere, and counting backwards for ten years
shows 7,344,000 pounds that have _gone_ somewhere—either up the flue or
down the flume.
The quantity of quicksilver distributed monthly among the mills shows
just how much is lost per month. None is sold or sent out of the country
in or with the bullion; therefore, if there were no loss, the mills
would never want any more quicksilver than enough to give them their
first start, as the same lot could be used over and over again, _ad
infinitum_.