of
sluices by which any one box may be removed for clean-up without
stopping the operation of the dredge. Platinum deposits in all parts of
the world are briefly discussed, with some notes on their relative
importance as possible producers and their analogies to the classic
Russian types.
Duparc
closes his paper with a brief review of the production and uses of
platinum and makes the statement concerning the Ural deposits that "the
reserves appear to be sufficient for about 12 years, if no new dredges
are built, and if the methods of working remain approximately as
to-day." He points out the prime necessity of platinum in various
industries, and concludes that "it will be necessary at once to
discover new deposits that will be able to make up for the lessening
production of the Urals."
SPAIN.
Notes
concerning the discovery of platinum in the Sierra de Ronda, in
southern Spain, were given in the report on platinum for 1915. Detaded
descriptions of these deposits by the discoverer, Don Domingo de
Orueta, have been published.1 In some respects the Spanish deposits resemble those of Russia, but Duparc and Gros-sett2
have emphasized the distinctions between the classic dunitic and
pyroxenitic Uralian primary deposits and the peridotitic type found in
the Si'erra de Ronda.
The
Russian primary deposits are essentially of magmatic origin and show a
gradation from feldspatnic rocks to the very basic chro-mite-olivine
rock dunite, whereas the Spanish primary deposits are in rocks composed
of rhombic pyroxene characterized by spinel with some gradations into
dunitic phases.
The
secondary (placer) deposits are also very different. The Russian
platiniferous gravels are in large part old and have been reworked by
the present streams. The topography is subdued, and the region is, in
fact, nearly a peneplain. The Spanish platiniferous gravels, on the
contrary, occupy steep-walled, young valleys. In the Russian deposits
practically all the platinum is found in the bedrock gravels, which are
distinct from the two overlying beds, but in the Spanish deposits there
is a gradation from coarser to finer gravels from surface to bedrock,
and, while there is slightly more platinum near bedrock than in the
upper part of the gravels, there is no sharply marked pay bed.
Details concerning the most recent work on these deposits 3 indicate that some areas will be found of workable grade.
TASMANIA.
The
osmiridium fields, 20 miles west of Waratah on Nineteen Mile Creek, a
tributary of Savage River, were worked in 1916 and produced 222 ounces
of crude metal. No information is available to indicate whether the
primary deposits described by Twelvetrees 4 have been exploited.
i Revista Min., Nov. 8,1915, No. 2519: Comp. Rend. January 1916.
2 Duparc,
Luis, and Grossett, Augustine, Etude compared des gites platiiiiferes
de la Sierra de Ronda et de l'Oural: Soc. phys. et hist. nat. Geneve
Me'm., vol. 38, fasc. 5,1916.
3 Commerce Repts., May 5,1917, pp. 476-477.
* Twelvetrees, W. H., The Bald Hill osmiridium field: Tasmania Dept. Mines Geol. Survey Bull. 17, 1914.
