Quicksilver is very costly, and they never waste it. On opening the
retort, there was our week's work--a lump of pure white, frosty looking
silver, twice as large as a man's head. Perhaps a fifth of the mass was
gold, but the color of it did not show--would not have shown if two
thirds of it had been gold. We melted it up and made a solid brick of it
by pouring it into an iron brick-mould.
By such a tedious and laborious process were silver bricks obtained.
This mill was but one of many others in operation at the time. The first
one in Nevada was built at Egan Canyon and was a small insignificant
affair and compared most unfavorably with some of the immense
establishments afterwards located at Virginia City and elsewhere.
From our bricks a little corner was chipped off for the "fire-assay"--a
method used to determine the proportions of gold, silver and base metals
in the mass. This is an interesting process. The chip is hammered out
as thin as paper and weighed on scales so fine and sensitive that if you
weigh a two-inch scrap of paper on them and then write your name on the
paper with a course, soft pencil and weigh it again, the scales will take
marked notice of the addition.
Then a little lead (also weighed) is rolled up with the flake of silver
and the two are melted at a great heat in a small vessel called a cupel,
made by compressing bone ashes into a cup-shape in a steel mold. The
base metals oxydize and are absorbed with the lead into the pores of the
cupel.
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