Thursday, December 3, 2009
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.
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
Total: 55 million carats
Old annual: 50,000 to 300,000 carats; 1730s to 1861
Today: 1.5 million carats