56

ECONOMIC GEOLOGY

occurs with ultra-basic rocks, as in the Urals, and in quartzveins.
 It is widespread in the Eastern Highlands of Australia
 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 sedimentary
 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 ultrabasic
 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 consist
 of pre-Paleozoic gneiss, schist, and quartzite, followed by
marine Devonian, Carboniferous and Permian. The igneous