|
744 MINERAL RESOURCES, 1918—PART I,
|
||
|
|
||
|
tion
during the year, these figures record the actual production of gold and
silver bullion from domestic ores in marketable form as metals, either
refined or unrefined.
Owing
to the difficulty of tracing this total gold and silver production
back to its origin by States, counties, and mining districts, however,
the Geological Survey attacks this problem of distribution by
systematic investigation of the mine production of ores containing
gold and silver during the calendar year and of the output of the
placer mines. In this way the state of the mining industry is studied
in detail, and the output is classified by methods of production and by
kinds of ore, as well as by mining districts. The resulting figures
form the basis of the mines reports.
Of
the two plans outlined for ascertaining the gold and silver production
of the United States it may be said that one is a measure of the mining
industry and the other a measure of the metallurgic industry; that one
reports the mine output and its recoverable content and the other the
metal actually recovered in marketable form. The two methods will not
produce exactly corresponding results, nor should they be expected to
do so.
The
figures of the reports of the mint and of the mines reports for a
period of years sufficiently long to compensate for overlap or lag
should agree within allowable limits of error due to the complexity of
the problem involved.
For the last 14 years in which complete statistics iiave been gathered by both methods the final figures have been as follows:
|
||
|
|
||
|
|
||
|
|
||
|
These
figures show, according to Mint reports, a total excess of gold for the
14 years of $9,346,997, or a difference of about 0.7 per cent, and a
total deficit of silver of only 4,100,781 ounces, or a difference less
than 0.5 per cent. The figures for Alaska placers are not considered to
be so closely approximate as the total figures for gold, hence the
differences for the United States proper are probably even lower. It is
thought that those small differences are fully accounted for in the
detailed discussions of the subject in previous reports of this series.
For figures of any one year an excess of mining over smelting and
refining is indicated by larger returns in the mines
|
||
|
|
||