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MINERAL RESOURCES, 1914----PART I.
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The
veins of pyrrhotite which intersect the serpentine which is associated
with these lodes must be of magmatic origin, and the serpentine is so
intimately mixed with the siliceous and metalliferous veins that mere
assay results may be misleading when one seeks the precise derivation
of the osmiridiuui obtained. The latter may be genetically connected
with the serpentine which is traversed by the veins, and not with the
veins themselves. This is probably the case, as osmiridium must have
separated out from the magma as one of the earliest minerals.
The
placers of Savage River were worked for gold as early as 1884, and when
the price of osmiridium rose in 1899 the miners began to save this
material. It was found that the osmiridium came from the streams
heading in Bald Hill, and it was later shown that it came from the
serpentine.
The
osmiridium, in some deposits coated with iron oxide, in others inclosed
in grains of chromite, is not always recognizable in the pan until
cleaned with acid. A peculiarity of the Tasmanian material is that it
contains almost no platinum, as shown by the following analysis,
published April 3, 1914, as an addendum to the report of Mr.
Twelvetrees.
Results of examination of half an ounce of osmiridium grains.
1. Mineralogical.—The
sample consisted of loose metallic grains, varying in color from
tin-white to yellowish gray. Half of the grains averaged about 1
millimeter in diameter and the remainder about one-half millimeter.
2. Chemical.—
Per cent.
Platinum (Pt)________________________________________ 0.37
Ruthenium (Ru)_____________________________________ 8.19
Palladium (Pd)______________________________________ .21
Gold (Au)__________________________________________ .04
Iron (Fe)_________________....._______________________ .30
Copper (Cu)______________ __________________________ Trace.
Iridium (Ir) and rhodium (Rh)________________________ 33.80
Osmium (Os) (by difference)--------------------------------------- 57.09
100.00
3. Commercial valuation and remarks.—The
above analysis indicates that the sample consists of iridosmine
(siserskite), in which the amount of osmium present is considerably in
excess of the iridium, the reverse being usually the case in the
analysis of iridosmium from other sources already on record.
Some additional details of the Tasmanian osmiridium fields were published late in 1914,] but the Government geologist's report described the principal features of this interesting district.
DETERMINATION OF PLATINUM.
Since
the unexpected and remarkable discovery of platinum in the ore of the
Boss mine in Nevada there has doubtless been more interest in
prospecting for this metal in lode deposits than ever before. The assay
for platinum, as is well known, is a delicate and difficult matter,
and not all assayers are thoroughly familiar with its technic. It is
possible, therefore, that some persons have been misled by incorrect
analysis of materials into the belief that they have workable platinum
lodes. On the other hand, platinum may be present, but not recognized.
In order to distribute more widely information concerning
1 Dunn, B. J. Tasmanian osmiridium fields: Australian Statesman and Mining Standard, Dec. 24, 1914, pp. 539-540.
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