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When diamonds were discovered by alluvial gold miners in Brazil in 1725, Indian diamond sources were near exhaustion and European demand for the stone continued unabated. From 1730 to 1870 Brazil was the world's major source of diamonds. Indeed, mining in Brazil was so active that by the late 1730s production far exceeded demand, and diamond prices fell by as much as 70%. Beginning in 1850, production rose again, following the discovery of rich deposits in Bahia, but after 1861 it rapidly declined as deposits were depleted, leading to a great shortage of rough diamonds in the European cutting centers in the late 1860s.
With
mine officials nearby, Brazilian slaves wash the gravel from riverbeds to concentrate the denser minerals in which diamonds are found. Dependency on slave labor was an unfortunate part of early diamond mining in Brazil. "Diamond washing in Brazil." Published in 1884. click to zoom in
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Productive Brazilian diamond deposits are all secondary. They are usually small, and some are of low grade, so mines typically operate for short periods. Primary diamond pipes exist but are generally uneconomic, suggesting that erosion has stripped away the richest portions from them. In 1890 and 1901, secondary diamond deposits were discovered in Guyana and eastern Venezuela, adjacent to deposits in Brazil's northern state of Rora’ma. Since 1890, Guyana and Venezuela have produced a total of about 4.5 and 14 million carats, respectively.
This map shows that diamond deposits are widely distributed in Brazil. Those in the states of Minas Gerais, Bahia, Mato Grosso, and Rora’ma have been the most important. The shaded areas are diamond deposits.
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Brazilian Production:
Total: 55 million carats
Old annual: 50,000 to 300,000 carats; 1730s to 1861
Today: 1.5 million carats
"Diamond washing in Brazil": Courtesy New York Public Library
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