The
origin of the Brazilian diamonds is not well understood. They do not
appear to have originated, like those of South Africa, in eruptive
rocks, as there are little or no traces of such rocks now to be seen.
They were formerly supposed to be constituents of a quartz schist,
called itacolumite, from Itacolumi, a prominent mountain peak
near Diamantina, but this is not now believed to be the case. The
present Director of the Geological Commission of Brazil, Orville A.
Derby, is of the opinion that the diamonds may have been formed out of
the carbon contained in the phyllites (clay schists) of the region by
the intrusion in them of pegmatite veins.
The
quantity of diamonds now obtained from Brazil is comparatively small,
the total production in 1880 being only about forty pounds (80,000
carats). During the past few years an extensive drought has prevailed
in the diamond-bearing regions, which has favored search for the stones
and increased the output. It is difficult at any time, however, to
learn the exact production, since there is much smuggling, owing to
the high duty of sixteen per cent levied on exported diamonds.
The
largest diamond from Brazil that is now known is that called "Star of
the South," which weighed in the rough 254.5 carats, and after being
cut, 125 carats. This was found in 1853 by a negro slave woman. It was
a dodecahedron, and has a peculiarity that no other diamond possesses,
in giving off in certain lights a rose tint, although perfectly white
itself. It was sold for one hundred and seventy-five thousand dollars
to a Paris syndicate, which is said in turn to have sold it to an
Indian prince.
The
next great deposit of diamonds to be found after that of Brazil, and by
far the most important known to-day, is that of South Africa.
The
first discovery of diamonds here is to be credited, as has so often
been true in the finding of gems, to the picking up of pretty stones by
children. Among such pebbles gathered by a child of Daniel Jacobs, a
Boer farmer living near the present town of Barkly West on the Vaal
River, one was thought by John O'Reilly, a roving trader, to be a
diamond. To test the matter he sent the stone to Dr. Atherstone, a
mineralogist at Grahamstown, who at once identified it as a veritable
diamond, and expressed the belief that more were likely to be found in
the region. This find was made in 1867, but no more diamonds were
discovered until March, 1869, when a superb stone weighing 83-1/2
carats, and which not long after brought a price of one hundred and
twenty-five thousand dollars, was picked up in the same region. This
discovery was sufficient to set a tide of diamond-seekers toward
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