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Brazilian Diamonds. 107
The
Portuguese, however, turned the tables, and sent the Brazilian Diamonds
to Goa, and thence to Bengal where they were offered for sale as Indian
stones, and obtained Indian prices.
It
is only within the last few years that the Diamond-bearing rocks of
Brazil have been sufficiently studied to enable geologists to speak
with anything like confidence, in regard to their nature and their age.
They have now, however, been thoroughly examined, especially by Prof.
Gorceix, the head of the School of Mines at Ouro Preto, the capital of
Minas-Geräes, and by Prof. Orville A. Derby, of the Geological Survey
of Säo Paolo. Sections have been made of the strata, of which the
Diamond-bearing provinces are composed, and a satisfactory sequence has
been established.
The
mode of occurrence of Diamonds at Diamantina, (formerly called Tejuco),
in the province of Minas-Geräes may fairly be taken as typical of the
workings throughout the country. It was here that Diamonds were
originally discovered in Brazil, and it was to this district that the
workings were for a long time restricted. Diamantina itself is situated
along the crest, and on both flanks of the great interior mountain
range of Brazil, which, at a general height of about 4,000 feet above
the level of the sea, divides the waters of the Sâo Francisco on the
west, from those of the Doce Jequetinhonha and other rivers on the
east. The northward prolongation of the range includes the Diamond
regions of Grào Mogol, in the province of Minas-Geräes, and that of the
so-called Chapada Dia-mantina in Bahia.
A
very important group of rocks stretches from the former to the latter
of these rivers. This group has been called the Itacolumite series,
from the occurrence of
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