a number of mines or by some simple, economical additional concentration process that could be developed at the mine.
As
much of the crude platinum produced in the United States is recovered
by dredges, it would be interesting to know what proportion of the
platinum content of the gravels is actually saved on the dredges. So
far as the writer is aware, no estimates of this saving are published.
In fact, little is published and perhaps little is known of the actual
recovery of gold and platinum by dredges. As pointed out by Janin1
the estimation of dredge recovery is a difficult matter, because, in
the first place, the actual mineral content of the gravel dredged is
difficult to arrive at; and, in the second place, it is still more
difficult to obtain satisfactory information concerning tailing losses.
Of the average gold content indicated by prospecting, 75 to 80 per cent
is usually considered recoverable by dredges, but the actual recovery
of the content may be greater or less than these percentages.
It would seem that there is considerable loss of flour gold and platinum in dredge operations. Neill2
has described an installation of jigs in the sluice fine of a dredge on
Merced River, which demonstrated their value in saving fine gold. That
this idea has met with some consideration is shown by the fact that
recently the Natomas No. 7 dredge, near Folsom, has been equipped with Neill jigs of which Eddys
says: "The recovery by this process has already been proved to reduce
the value of the tailings of No. 7 dredge to a negligible amount." The
concentrates from these jigs are ground in a Hardinge mill, and the
pulp is passed over a shaking amalgamator and finally over a
silver-plated amalgam plate before being discharged. It is said that 97
per cent of the recovery from the tailings is made in the Hardinge mill
and the shaking amalgamator.
Whether
platinum is saved by this installation is not stated, but the
probabilities seem to favor the use of some such treatment of fines on
dredges which are known to be digging gravels containing gold and
platinum.
ELECTROLYTIC REFINING OP GOLD AND COPPER BXTLLION.
There are in the eastern United States at least nine copper refineries that recover platinum and palladium from blister copper.
There
are also in the United States a number of plants that treat chiefly
platinum metals, recovering them both from crude platinum and from
"sweeps" from dental works and manufacturing jewelers' establishments.
Some of the more important buyers of crude platinum and sweeps are
listed below.
American Platinum Works, Newark, N. J.
Baker & Co. (Inc.), Newark, N. J.
J. Bishop & Co., Malvern, Pa.
Commercial Research Co., Long Island City, N. Y.
Thomas J. Dee & Co., Chicago, 111.
Elizabethtown Smelting Co., Newark, N. J.
Goldsmith Bros. Smelting & Refining Co., Chicago, 111.
Pacific Platinum Works, Los Angeles, Cal.
Roessler & Hasslacher Chemical Co., Perth Amboy, N. J.
S. S. White Dental Manufacturing Co., Philadelphia, Pa.
i
Janin, Charles, Recovery of gold in dredging: Min. and Sci. Press, vol.
109, pp. 717-721, Nov. 7,1914. 2 Neill, J. W., Application of jigs to
gold dredging: Min. and Sci. Press, vol. 109, pp. 839-842, Nov.
28,1914. s Eddy, L. H., Jigs on a California dredge: Eng. and Min.
Jour., vol. 101, pp. 207-208, Jan. 29,1916.
