An
ordinary washing plant of this kind is capable of handling about 125
metric tons of sand in eight hours. The yield of the gravels is
variously stated at from 0.05 to 1 ounce per cubic yard.
Most
of the platinum from Russia is obtained in the manner just described,
but the method is not very efficient, and unless great care is taken
considerable quantities of fine platinum are lost in the tailings.
Platinum
mining in the Urals, however, has begun to feel the influence of modern
methods. Several years ago dredges were shipped in from abroad, and
attempts were made to work gravels on the properties of Count Shuvalov
and of the Platinum Mining Company. Owing to faulty construction and to
their unadaptability to conditions at hand, these dredges proved an
entire failure. But the experiments were persevered in and success has
finally been attained and has induced a rapid installation of dredges.
At
first the dredges were very expensive, as they had to be imported, but
now there are several companies in the Ural district that are
manufacturing dredges both cheaply and well, and that can supply any
demand of the mining companies. The machines closely resemble the
modern gold dredge in all their essential features, but have a few
modifications which adapt them to the different conditions with which
they have to deal.
In describing one of these dredges Mr. Purington says:
The
hull drew 5 feet of water, and was well constructed of pine. The
digging ladder was of iron. and provided with 46 4-foot buckets having
lips of manganese steel. The ladder was designed to dig to 35 feet.
"Water was supplied by a centrifugal pump. The dredge was moved by
winches and cables, no spuds being used. The washing apparatus
consisted of a trommel for taking out the coarse material, from which
the fines went to two tables with baek-to-back arrangements fitted with
riffles and mats. The intention was to use no quicksilver in the
saving. The stacking ladder was considerably shorter than those
generally in use in America. The power was steam, only 50-horse-power
boiler and engine being provided. The fuel used was peat. The capacity
of the dredge was estimated at 80,000 poods of gravel (about 1,000
cubic yards) per twenty-four hours. The cost of handling the material
was estimated at 5 cents (2 doli in fine gold) per cubic yard. The
dredge was to be worked by four men on a shift, three eight-hour shifts
per day. The cost of the dredge was given to the writer, and was
surprisingly low, but as the dredge was not for sale, and the figure
given represented the actual cost of building, the publication of it
would be unfair to the manufacturers.
There
are many localities, especially along the lower Iss and Tura rivers,
where conditions appear very favorable for dredging operations.
Whatever
measure of success dredging may attain it will not entirely supplant
other methods of mining platinum any more than it has supplanted other
methods of mining placer gold, but at present the indications point to
a considerable development of the industry along this line.
UNITED STATES.
In
the United States the mining of platinum is slowly advancing from its
hitherto obscure position, and bids fair in the immediate future to
occupy a much more important place among the mining industries of the
country. This condition of affairs has been brought about largely as a
direct result of the tests and experiments conducted by the United
States Geological Survey at Portland, Oreg., in connection with the
Lewis and Clark Exposition at that place in 1905. These experiments,
which were conducted under the immediate supervision of Dr. David T.
Day, of the Survey, have succeeded in establishing two facts: First,
that the platinum-bearing gravels of this country are of no mean extent
nor small value, and, second, that the methods by which the best
results in working the deposits may be obtained have been clearly
pointed out.
It is with these methods that we are here principally concerned.
Up
to the present time the small quantities of the platinum metals
produced in this country have been obtained, as already stated, as
by-products in washings where the recovery of gold from the gravel or
sand was the primary object. In such cases
