Datas is a historic diamond-mining locality situated in the Diamantina region of Minas Gerais, Brazil, whose name derives directly from the Portuguese administrative term for the parcels of land — datas, meaning 'allotments' — granted to individual miners under the colonial Portuguese licensing system. Active principally during the eighteenth and nineteenth centuries, Datas formed part of the broader alluvial diamond field centred on the town of Tijuco, today known as Diamantina, and contributed meaningfully to Brazil's emergence as the world's dominant diamond-producing nation during a period when the Indian supply from Golconda was in steep decline. The locality is documented in gemmological literature, including Gems & Gemology, as one of the constituent deposits of the Minas Gerais alluvial system.

Geological and Geographical Setting

The Diamantina region occupies the high chapada — the plateau country of the Espinhaço mountain range in central Minas Gerais — where ancient Precambrian conglomerates and quartzites of the Espinhaço Supergroup host primary and reworked diamond occurrences. Diamonds in this system are believed to have been liberated from these ancient sedimentary host rocks by prolonged weathering and fluvial transport, ultimately concentrating in alluvial gravels along river valleys and in colluvial deposits on hillslopes. The precise primary kimberlitic or lamproitic source of the Diamantina diamonds has never been definitively identified, a geological puzzle that persisted through the colonial era and into modern research.

Datas itself lies within this broader geological province, its gravels representing reworked concentrations of the same population of diamonds found at Tijuco and along the Rio Jequitinhonha drainage system. The diamonds recovered from the Datas allotments were typically recovered by washing and sieving of loose gravel — a technique the Portuguese colonial administration organised using enslaved African labour on a large and systematised scale.

Colonial Administration and the Data System

When diamonds were first officially recognised in the Serro Frio district of Minas Gerais around 1725, the Portuguese Crown moved swiftly to assert control over what was immediately understood to be an enormously valuable resource. The administration of the diamond fields underwent several phases of organisation, but central to the colonial system was the division of productive ground into discrete parcels known as datas. Each data was a measured allotment of mining ground granted — initially by licence, later under the direct monopoly of the Distrito Diamantino — to an operator who was required to pay a per-carat royalty or a fixed contract sum to the Crown.

The Distrito Diamantino, formally demarcated in 1771, imposed strict controls on movement, trade, and settlement within its boundaries. Residents required special authorisation; the export of diamonds outside official channels was a capital offence. This administrative apparatus, though frequently circumvented by smugglers, gave the Portuguese Crown an unusually tight grip on production and, for a time, on world diamond prices. The locality name Datas thus encapsulates the entire administrative philosophy of the colonial diamond enterprise: the landscape itself was conceived as a grid of productive allotments to be licensed, worked, and taxed.

Diamond Characteristics

Brazilian diamonds from the Diamantina region, including those recovered from the Datas allotments, are generally alluvial stones that have undergone considerable natural abrasion and sorting. They tend to be well-rounded crystals and fragments, frequently octahedral or dodecahedral in habit, and are noted for a high proportion of colourless to near-colourless material alongside a significant occurrence of fancy colours — most notably yellow, brown, and the rare and celebrated blue stones for which the Brazilian fields achieved particular renown in the eighteenth century.

The blue diamonds of Minas Gerais, coloured by the presence of boron, attracted intense European interest and several notable specimens entered royal and aristocratic collections of the period. The most famous stone associated with the broader Minas Gerais alluvial system is the Hope Diamond, whose Brazilian origin has been proposed by some researchers, though the precise locality of its recovery — whether Datas, Tijuco, or another part of the field — cannot be established with certainty from historical records.

Inclusions typical of Minas Gerais alluvial diamonds include graphite platelets, olivine, and garnet, consistent with a mantle-derived source, though the absence of a confirmed primary pipe means that inclusion studies have not been tied to a specific kimberlite chemistry in the way that, for example, Argyle or Jwaneng diamonds can be fingerprinted.

Historical Significance and Market Impact

The discovery of diamonds in Minas Gerais in the early eighteenth century had profound consequences for the global gem trade. Prior to the Brazilian finds, India — specifically the Golconda region of the Deccan — had been the sole significant source of gem diamonds known to European markets for centuries. The sudden availability of Brazilian material, initially smuggled through Goa to disguise its origin and protect Indian market prices, eventually flooded European markets and effectively ended Golconda's dominance.

At the height of Brazilian production, the Diamantina field — of which Datas was a constituent part — was yielding tens of thousands of carats annually. Production figures varied considerably depending on the administrative regime in place: the contract system, the Crown monopoly under the Junta da Administração do Distrito Diamantino, and later the post-independence Brazilian state each managed the fields differently, with corresponding fluctuations in recorded output.

Brazilian dominance of world diamond supply lasted until the late 1860s, when the discovery of primary kimberlite pipes in South Africa — first the alluvial deposits along the Orange and Vaal rivers, then the great pipes at Kimberley — shifted the centre of gravity of the diamond world decisively to southern Africa. Brazilian production continued, but at a scale that could not compete with the industrialised mining of the South African pipes.

Legacy and Present Status

Diamantina was inscribed as a UNESCO World Heritage Site in 1999, recognised for its exceptional colonial urban fabric and its direct association with the diamond-mining history of the region. The town preserves much of its eighteenth-century architecture, including the former administrative buildings of the Distrito Diamantino, and serves as the principal cultural and historical reference point for the entire alluvial field.

Artisanal diamond mining continues in parts of Minas Gerais, including areas associated with the historic Datas allotments, though production is modest by global standards. The region is of greater significance today as a subject of historical and gemmological study than as a commercial source. Researchers interested in the provenance of historic diamonds — particularly those that entered European collections in the eighteenth century — continue to examine the Diamantina field, including Datas, as a potential origin for stones whose early histories are incompletely documented.

For the gemmologist and gem historian, Datas represents more than a single locality: it is a metonym for the entire colonial system of allotted, licensed, and taxed diamond extraction that shaped both the physical landscape of the Espinhaço highlands and the commercial structure of the eighteenth-century diamond trade.

Further Reading

• Gems & Gemology — GIA Publications Archive
• GIA: Diamonds from Brazil