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GOLD AND SILVER.
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115
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MINES REPORT.
METHOD OF COLLECTING STATISTICS.
It
should be distinctly understood that the table on page 3 contains the
figures of the production of gold and silver which are accepted as
final by the Geological Survey, inasmuch as they record in the main the
quantities of these metals which were actually produced during the
calendar year. It is difficult to trace the refined metals back to the
States where the ore was produced, and it is still more difficult to
trace them back to the producing counties and districts. In order,
therefore, to ascertain the state of the mining industry in each mining
camp, the Geological Survey asks the owners of each mining property to
report the amount of gold and silver, as well as that of other metals
produced. Tabulated in proper form, these replies form the basis of
this mines report.
The
Mint Bureau records the production of the precious metals from gold
bullion deposits in United States mints and assay offices, from the
fine bars reported by the refineries, and from the gold and silver
contained in ores and metallurgical products exported for reduction.
The
statistics of gold and silver collected from the mines by the
Geological Survey are obtained from the following 4 items: 1. Gold and
silver in placer bullion produced during calendar year. 2. Gold and
silver in mill bullion produced in mill of company during calendar
year. 3. Gold and silver in base bullion, matte, etc. (by assay value),
produced in smelter of company during calendar year. 4. Gold and silver
in crude ore and concentrates (by assay value) shipped to custom works
in calendar year.
The
first item needs no explanation. The second and third items cover the
cases of mining companies which have their own reduction works; they
report the gold and silver bullion produced during the year, or the
gold and silver contained in their metallurgical products sold to
refineries, as they are very few smelting works owned by mining
companies which also refine their base bullion. There is, as a rule, no
great interval of time before the ore sent to these mills and smelters
is reduced to gold and silver or base bullion, and, although there is
some overlap at the beginning and close of the year, the tonnage
shipped from the mine during the year corresponds with fair accuracy to
the quantity of fine or base bullion or matte produced.
The
greatest difficulties are found in the fourth item, comprising ores and
concentrates shipped to custom works—generally smelters, more rarely
mills—as a considerable interval of time, often thirty days or more,
elapses before the ore reaches the works, and often much more before it
is reduced and refined. It is mixed with other ores and loses its
identity, and the assay value is the only guide the miner has to the
quantity of metal produced. In these cases the miner is requested by
the Geological Survey to give the tonnage and assay value of ores and
concentrates shipped up to the end of the year.
It should be emphasized that the table of mine production does not give the contents of the ore mined during the year. Only the ore that is treated or sold is recorded. Neither does this report give
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