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DIAMOND MINES OF BRAZIL 197
rounding of the crystal edges and the diminution in size and weight of the pebbles carried along from stage to stage.
Although
there is a general resemblance between the material of the several
districts of Brazil in which diamonds are found, it is probable that
the sources are separate formations, as there are distinct differences
in the number and quality of the accompanying minerals, and the
diamonds themselves differ in shape and character. The grupiaras of
the Pardo district are similar to those of the Diamantina district of
Minas Geraes, and they each contain quartz, yellow and red fragments of
monazite crystals, white and brown zircon, cyanite, staurolite,
almandine, titanite, magnetite, and pyrite, but corundum, which is
found in no other Brazilian diamond field, occurs with the diamonds in
the Pardo district. On the other hand, the Pardo fields are said to
contain no anatase, tourmaline, hydro-phosphate or itacolumite. The
diamonds also, unlike those of other fields, are octahedral, whereas
the usual form of Brazil stones is cubic. In the Paraguassu district,
the crystals are irregular and distorted; in Minas Geraes they are
regular and cubic; in the Pardo fields, regular and octahedral. The
diamonds of the Paraguassu, where carbons are found with them, though
more brilliant, are not as clear as those of the Cannavieiras or Pardo
region, where carbons do not occur. There are other differences.
Bagagem yields the largest and best crystals. The crystals of the
Bahia fields run smaller than those of Minas Geraes and carry more
color. It is a peculiar fact that many of the colored Brazilian
crystals cut white, even of those which in the natural state appear
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