In the Uryanchai district of Mongolia, situated on the Russian border, deposits of auriferous gravels have been worked on a fairly extensive scale for some time past. It was announced a few years ago that platinum and iridium had been found in appreciable quantities, associated with the gold, some large platinum nuggets being obtained from this region in 1911. Although no attempt at commercial development has yet been made, the prospects of profitable extraction appear to be hopeful. Extensive outcrops of olivine rocks have been noticed in the vicinity, and the nature of the occurrence is stated to bear some resemblance to that of the platiniferous fields of the southern Urals[[8]] p. 107.
Japan
Platinum occurs in the Yubari-garva, Pechau and other rivers in the province of Hokkaido. It is also found in Nishi-Mikawa, province of Sado. In the former locality gold and iridosmine are associated with the platinum, and in the latter gold and iron sands are present[[62]]. In no case has the metal been traced to its parent source. In the Hokkaido deposits the average quantity of platinum present is only 2 or 3 per cent. of the iridosmine content. It is possible that further exploration in these areas will reveal occurrences of greater importance[[9]] p. 597.
Sumatra
Platinum is obtained at Sipongi, where it occurs with wollastonite and grossularite in limestones and schists, near intrusions of granodiorite and augite diorite. Gold is also present.
L. Hundeshagen[[61]] is of opinion that the present ore deposit was originally a layer, or a big lens, of limestone embedded in the old schists, which has, by apophyses of granite, been altered into garnet and wollastonite, being at the same time, or very soon afterwards, mineralized by hot solutions carrying copper, gold, platinum, etc. A sample of slightly decomposed wollastonite with no copper, or only minute traces of that metal, proved to be richest in platinum, the assay showing 6 gm. of platinum per 1,000 kg., while samples with 2 to 10 per cent. of bornite and malachite contained only traces of platinum; and none could be detected in auriferous garnet, poor in wollastonite. About 10 to 25 metres from the outcrop the concentrated river sand shows small particles of whitish crystalline gold and rounded grains of white platinum, the latter varying from 0·1 to 0·3 mm. in size.
AFRICA
Congo Free State
In the Katanga district, platinum and palladium have been reported to occur in certain alluvial gravels, accompanied by gold and silver. One sample from this locality is stated to have yielded the following amounts per metric ton: 3·4 gr. platinum, 12·3 gr. gold, 8·3 gr. silver. It has also been located in situ in sandstones containing gold.