Minas Velhas — The Old Mines of Brazilian Diamond Production
Minas Velhas — The Old Mines of Brazilian Diamond Production
The eighteenth-century alluvial diamond fields of Diamantina before South Africa
Minas Velhas — Portuguese for old mines — is the historical term used in the Brazilian diamond trade and in the gemmological literature to refer to the eighteenth- and early-nineteenth-century alluvial diamond workings of the Diamantina region in central-northern Minas Gerais state. The term distinguishes the early Brazilian production from the South African finds that came on stream after 1867 and from the later mechanised Brazilian operations of the twentieth century. Minas Velhas diamonds dominated global supply for nearly 150 years and have a recognisable place in historical jewellery collections and in early-modern European gem inventories.
Discovery and the colonial period
Diamonds were first identified in the gravels of the Jequitinhonha River and its tributaries in the early 1720s, in territory that the Portuguese colonial administration of Brazil had been working for gold for several decades. Initial discoveries were made by gold prospectors who had been treating the small white crystals as worthless before someone — the historical record is uncertain on the exact identification — recognised them as diamonds. The recognition transformed the regional economy almost overnight.
By the 1730s the Portuguese crown had imposed a strict monopoly on diamond extraction, organising the production through the Demarcação Diamantina (Diamond District) administered from a fortified compound at the town that would later become Diamantina. The monopoly system used both contracted production and direct crown-managed mining; smuggling was a constant problem and the system imposed severe punishments — including transportation and execution — for unauthorised trading. The diamond district was effectively a closed police territory through much of the eighteenth century.
The output and its global significance
At its eighteenth-century peak, Brazilian production from the Minas Velhas was supplying virtually all the diamond reaching European markets. The major Indian fields at Golconda and Panna had been in long decline by the time the Brazilian production came on stream, and Brazilian material rapidly displaced Indian as the principal source. The Brazilian diamonds were typically alluvial in origin — recovered from river gravels rather than from primary kimberlite, which was not understood as a diamond source until the South African discoveries — and they tended to run smaller in average size than the Indian production but in considerably greater volume.
Major historical pieces of Brazilian provenance include the 90-carat Star of the South (recovered in 1853 and cut down to a 128-carat stone after re-fashioning) and various pieces in royal collections that pre-date the South African production by decades or centuries.
Decline and the modern usage of the term
Brazilian diamond production declined sharply after the South African discoveries beginning in 1867, both because the South African kimberlite output was an order of magnitude larger and because the South African production substantially lowered global diamond prices and made the alluvial Brazilian operations economically marginal. By 1900 Brazil was a minor producer; the Diamantina district continues to produce small quantities today but plays no role in global supply.
In current gemmological and historical literature, Minas Velhas is used principally as a provenance term for diamonds in historical collections that are documented or believed to have come from the eighteenth or nineteenth-century Brazilian production. The term is sometimes applied loosely to any Brazilian diamond predating the South African shift, but the strict usage refers to the colonial-era monopoly production. The word should not be confused with the modern Brazilian municipality of Minas Velhas, located in Bahia.