56 
ECONOMIC GEOLOGY 
occurs with ultra-basic rocks, as in the Urals, and in quartz- 
veins. It is widespread in the Eastern Highlands of Aus- 
tralia and is found in New Zealand. 
Platinum is usually obtained from alluvial deposits, in 
which it collects owing to its heaviness and resistance to 
weathering. Some alluvial platinum is derived from sedi- 
mentary rocks, as from slates in Germany and New South 
Scale In Miles 
cz 4 8 
— LB 
a] 
i 
- | 
Hg 
T 
5 
2) Tuffoig Schr. ephyrtes... FT23 
Dolomiti Umeszone, TTT Duke ant... EE pyronenite. SS otivine - Gatbro IZ Phas [52] Ata. L220) 
tower Devonian other feridotites 
Fic. 23.—THe PraTiNuM PLaceERs oF THE Is River. 
The platinum placers of the Is River, the Urals, after N. Vuisotzkii, 
1913. (Ghor = mountain} The district is around 582° N., 503° E. 
Nigha 
Wales; but most of it has been derived from basic and ultra- 
basic igneous rocks, and especially from the chromite-olivine 
rock, dunite. 
Urar MountaiNs—The platinum deposits of the Ural 
Mountains are the most important. Those mountains con- 
sist of pre-Paleozoic gneiss, schist, and quartzite, followed by 
marine Devonian, Carboniferous and Permian. The igneous