The silver state. [volume] (Winnemucca, Nev.) 1909-1925, 1918-02-12
IDEAS ON
new PROSPECTING


Because of the extreme high price
paid now for platinum, around $50 to
Sl10 per ounce, prospectors are giving
considerable attention to the quest for
this precious metal. A recent article
given out on this subject by j. NJ. Hill
of the Geological Survey, gives many
interesting pointers on prospecting
for platinum. He says:
Platinum is not known in all coun-
tries. but that all the deposits are
known is highly improbable. In fact,
platiniferous deposits in Southern
Spain have been discovered recently
by geologist working on the assump-
tion that the place to look for plati-
mum is in areas of basic igneous rocks
similar to the typical Russian rocks
Systematic search, based on similar
assumption, in all countries may lead
TO the discovery of new deposits of
platiniferous gravels of economic inn
portance, but note of warning
should be sounded. In Russia sucn
systematic work has been in progress
posits have been found they are not
so numerous nor so rich as the hope
of the explorers anticipated.
Platinum, both in the native metal
and in the form of sperrylite tplati-
mum arsenide) has been found in basic
igneous rocks in several places in the
world, but not in commercial quanti-
ties. The search fdr the source of
platinum in rocks is therefore not
likely to be of particular value in OBJ
tanning an immediate supply of the
metal from lode deposits. 1t may,
however, develop nearby gravel de-
posits. AS already stated, it is con-
fdently believed that any platiniferous
ores of commercial grade will yield
o the regular analytical treatment in
he hands of competent assayers.
The placer deposits containing plat
mum are all, SO far as known, in the
vicinity of areas of basic igneous
rocks, and it would seem that in
3earch for new deposits of platinifer-
5us gravels the first step is the search
or outcrops of peridotite, pyrozenite
dunite and serpentine. When areas
Of these rocks have been found, the
grayels of the streams rising in them
should be washed to ascertain if
platinum is present. The heavy con-
centrates found in grayels carrying
platinum are usually rich in chromite
and olivine. The character of the
rnck rffoIac nffap oIt1o 10
the source from which the gravels
were derived
Crude platinum, as it occurs in
placer concentrates, is ordinarily a
silvery white metal which could be
confused only with silver and possibly
pieces of iron or steel. 1t can be dis
tinguished from both of these metals,
as they are soluble in dilute nitric
acids crude platinum can be dis
solved only in concentrated aqua
regia. In some placer deposits the
grains of platinum are coated with
dark film and somewhat resemble the
grains of the dark minerals chromite,
magnetic, or immenite, from which
they are separated by careful pan
ming, as the specific gravity of plati-
mum is greater than that of any of
those minerals.
Platinum will not amalgamate with
quicksilver alone, but will amalga-
mate if sodium is added In ordinary
quicksilver amalgamation the flakes
of platinum float on the surface and
can be removed. If sodium amalga-
nation is used, the platinum may be
separated from gold by agitating the
amalgam with water until all the
sodium is used up to form sodium
hydroxide; then the platinum will
come out on the surface of the ANAL
gam, provided, of course, the amalgam
is sufficiently liquid. Platinum has a
hardness of 4 to and can be scratched
with a knife. 1t is so malleable that
il can be pounded without heating into
very thin sheets. 1t is practically in
fusible; the grains cannot be melted
together, as can particles of gold.