About 90 per cent of the world's crude platinum produced annually comes from the Ural Mountains in Russia. The deposits next in importance are those of Colombia. Small amounts are produced in New South Wales, Tasmania, New Zealand, Borneo, British Columbia, United States, India, and Spain; and as a by-product in the electrolytic refining of the Sudbury, Canada, nickel ores. The extension of this method of refining to all of the Sudbury ores would create an important supply of platinum. The Colombian output has been increasing rapidly since 1911. Meanwhile the Russian production has declined; and from the best information available, it is not likely that Russia will be able to maintain production for many more years. Estimates of the life of the Russian fields are from 12 to 20 years at the pre-war rate of production.
The platinum situation is commercially controlled by buying and mine-operating agencies,—the French having, before the war, practically dominated the Russian industry, while American interests controlled in Colombia. The situation is further influenced by four large refineries, in England, Germany, United States, and France.
Before the war the United States produced less than 1 per cent of the new platinum it consumed annually. Production comes principally from California, with smaller amounts from Oregon, Alaska, and Nevada. The many efforts which have been made to develop an adequate domestic supply of this metal do not indicate that the United States can ever hope to become independent of foreign sources for its future supplies of platinum.
There is little reason to doubt that the Colombia field, commercially dominated by the United States, holds great promise for the future. The output has come largely from native hand labor, and with the installation of dredges can probably be greatly increased.
During the war, the need for platinum for war manufactures was so urgent and the production so reduced, that restrictions against its use in jewelry were put into force in all the allied countries. The United States government secured quantities of platinum which would have been sufficient for several years' use if war had continued. With the cessation of hostilities restrictions on the use of platinum were removed, and the accumulated metal was released by the government from time to time in small quantities; but the demands for platinum in the arts were so great that prices for a time tended to even higher levels than during the war. More recently supply is again approaching demand.
Geologic Features
Platinum, like gold, occurs chiefly as the native metal. This is usually found alloyed with iron and with other metals of the platinum group, especially iridium, rhodium, and palladium. Most of the platinum as used in jewelry and for electrical purposes contains iridium, which serves to harden it. Paladium-gold alloys are a substitute for platinum, chiefly in dental uses.
The original home of platinum is in basic igneous rocks, such as peridotites, pyroxenites, and dunites, where it has been found in small, scattered crystals intergrown with olivine, pyroxene, and chromite. Platinum is very dense and highly resistant to oxidation and solution. In the breaking up and washing away of the rocks, therefore, it is concentrated in small grains and scales in stream and beach placers. Of the world production of platinum over 99 per cent has been derived from placers.
The Ural Mountain deposits of Russia are gold- and platinum-bearing placers, in streams which drain areas of dunite rock containing minute quantities of native platinum. The deposits of Colombia and Australasia are placers of a similar character. In the United States small quantities of platinum are recovered from the gold-bearing gravels of California and Oregon, where the streams have come from areas of serpentine and peridotite.
A platinum arsenide, called sperrylite, is sometimes found associated with sulphide minerals in basic igneous rocks. At Sudbury, Ontario, this mineral, together with palladium arsenide, is found in the nickel ores, especially in the weathered zone where it is concentrated by removal of more soluble materials. It has also been found in the copper mines of Rambler, Wyoming. In the Yellow Pine district of southern Nevada, metallic gold-platinum-palladium ore shoots are found in association with copper and lead ores, in a fine-grained quartz mass which replaces beds of limestone near a granitic dike. No basic intrusives are known in the district. The deposit is unusual in that it has a comparatively high content of platinum (nearly an ounce to the ton), and is probably genetically related to acid intrusives. From all these deposits, only small quantities of platinum are mined.