Reviews—Platinwm Deposits of the World. 185 
grains idiomorphic against the olivine, or, more usually, in 
segregations of chromite. When platinum is present in the 
pyroxenites, it occurs interstitially as the latest product of 
crystallization. 
It is well known that platinum never presénts itself in nature as 
a pure metal, but always in alloy with other members of the 
“platinum group ”’ and withiron. In the material studied, from the 
Urals and elsewhere, the authors distinguish among the constituents 
of the various mixtures five groups: iridium, osmides of iridium, 
palladium, platinum, and iron. The native iridium is rare, but 
‘‘ osmides of iridium ”’, often in rhombohedral crystals, form part of 
most of the crude platinum of the Urals. The term employed seems 
to imply the existence of definite compounds, and indeed two types 
are discriminated and named, but the chemical analyses show much 
variation. Palladium is extremely rare in the Urals, though often 
present in the South American platinums. The Russian native 
platinum, unlike the Brazilian, contains iron as its most important 
element after platinum, and two types are recognized: polyxene, 
with 6 to 10 per cent of iron, and ferroplatinum, with 12 to 20 
per cent, the latter being magnetic and of dark colour. The chemistry 
of the platinum group of metals is not without difficulties for the 
analyst. A discussion is here given of the various laboratory 
methods, and a large number of analyses are brought together. 
Since exploitation of platinum in its original home is manifestly 
out of the question, it is the more important to study the alluvial 
deposits from which it is actually procured. The authors find that 
the present distribution of the platinum is not always in accord 
with the existing drainage of the country. In the case of the Koswa 
river-system, that which is now found in the tributary streams has 
been derived from older deposits, laid down when the river flowed 
at a higher level and followed a different course. A full description 
is given of the methods practised in prospecting and working 
platiniferous deposits. Then follows a detailed description of the 
numerous occurrences in the Urals, with more summary notices 
of those of Ronda in Spain, El Choco in Colombia, Brazil, British 
Columbia, Borneo, and other countries. The last three chapters 
deal with the metallurgical processes for treating the crude platinum, 
the various industrial uses of the metal, and statistics of production. 
We learn that in a period of 92 years the deposits of the Urals have 
produced 231,664 kilos (316-4 tons), exclusive of the large quantity 
lost every year by theft. In 1911 Russia furnished more than 
93 per cent of the world’s supply, Colombia ranking second with 
6 per cent. Further exploration of the northern Urals, and especially 
of little known Colombia, may possibly lead to an enlarged output 
in the future, but it is certain that platinum can never be other than 
a rare metal. 
Embodying a large amount of original research and summarizing 
practically all that is known at the present date, this will doubtless 
