Platinum was discovered in south-eastern Borneo in 1831, in the gravels of Gunung Lawack, but for a long time the natives were ignorant of its value. In recent years it has been obtained on a small scale as a by-product in the process of gold-washing, carried on in the province of Tanah-Laut, in the south-eastern extremity of the island[59]. The deposits occur in streams, which rise in the Bobaris Mountains, where the country rocks are composed of schists and gneisses, intruded by serpentine gabbro and diorite dykes[52] p. 298. Platinum has, however, not yet been located _in situ_. In addition to gold, the platinum is associated with osmiridium in the gravels, the two former being frequently found intimately intergrown. The platinum content of the native metal has been found by a number of analyses to vary from about 57 to 83 per cent., and that of osmiridium from 0·18 to 10·07 per cent.[60]. The rare mineral _laurite_, a sulphide of ruthenium and osmium, was discovered in these deposits. According to L. Hundeshagen[61], the platinum occurring in the diamond placers of western and south-eastern Borneo is in the form of thin scales, ranging from 0·1 to 1·0 mm. in length. These platinum scales contain from 3·8 to 4·5 per cent. of copper, evidently as an alloy. CHINA 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.