CARBONADOS
The
carbonado, a dark variety of the diamond, is opaque, without a
clear-cut crystalline form, nearly always a yellow, dark gray or black
and is of great utility because of its extreme hardness. Although found
in Baia as early as 1842, no special importance was attached to these
carbonados until 1860, when Leschot discovered their utility in tipping
rock drills.
Up
to the present, carbonados have been found in economically favorable
conditions only in Brazilian fields. The carbonados coming from
Piranhas, in the municipality of Andarai in the state of Baia
generally obtain the best prices and have become the principal world
source for this stone.
The
United States is an important market for this industrial product.
American capitalists have organized an enterprise known as the
Companhia Brasileira de Exportac,ao Diamantina, a subsidiary of the
Baia Corporation, to exploit this stone. This company is the only one
which works carbonado deposits on a large scale with machinery for
extraction, washing and sorting.
In
1895 the largest carbonado in the world was discovered in Chapa-da
Diamantina. Its weight, according to some, was 2,078 carats and
according to others 3,167 carats. A model of it in iron is in the
National Museum in Rio de Janeiro. The carbonado in question was broken
up into stones for sounding equipment and played an important part in
the development of the mining district of Mesabi in the United States.
Production
of carbonados in Brazil approximates the exports of the state of Baia
inasmuch is it is the only producing zone in Brazil and in the world
and very little direct use is made of the stone locally. The total
exports of Baia in 1937 totalled 2,605,285 grams 12.7% of which was
shipped to Rio de Janeiro and 87.3% overseas. In 1938, the total had
decreased to 1,370 grams the percentage shipped overseas in this year
being 69% and that to Rio de Janeiro 31%. The 1939 shipments increased
to 3,163 grams, 2,202 grams of which were shipped to Rio de Janeiro
and 961 grams! directly overseas the larger part of which was to
London. The 1940 shipments amounted to 2,762 grams, 2,263 grams being shipped to Brazilian markets and the remainder to the United States and England.
Carbonado
exports have never reached the levels of the 1920-9 decade in which
they amounted to an average of 6,386 contos. Since 1936, there were
indices that the industry was on the way to recovering its former
importance and in 1940 totalled 1,180 contos after being at the low of
62 contos in 1936. In 1937, England acquired 103 contos of the total of
165 contos that Brazil exported in that year. In 1938, and 1939,
Germany proved to be the ' largest market of these diamonds by
purchasing 275 contos of the total of 509 contos in the former year and
378 contos of the 1,021 contos in 1939. Belgium was the second largest
market for carbonados in 1938 purchasing 102 contos of this stone but
in 1939, the United States was second, her total being 374 contos. In
1940, the United States was the principal market by accounting for 691
con-
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