The Krishna River Valley, in the present-day Indian states of Andhra Pradesh and Telangana, was for two millennia the principal source of the world's diamonds. From the early centuries of the common era until the eighteenth-century rise of Brazilian production, virtually every important diamond known in the West and the Islamic world had passed at some point through the alluvial workings of the Krishna and its tributaries.

Geography and geology

The Krishna rises in the Western Ghats and flows east-south-east through the Deccan Plateau before discharging into the Bay of Bengal. Diamondiferous gravels were worked along several reaches of the river and its tributaries, most importantly around Golconda (now part of Hyderabad), Kollur (Telangana, Guntur district), Partial, Wajra Karur, and the Anantapur-Kurnool tract south of the river. The diamonds were transported by ancient drainage systems from kimberlite intrusions of the Wajrakarur and Banganapalle fields and concentrated in conglomeratic horizons later reworked by rivers. Most extraction was alluvial, conducted by hand-pit and gravel-washing methods worked by hereditary mining communities under the patronage of local rulers.

Historical importance

The Kollur mines produced many of the great named diamonds in history, including the Koh-i-Noor, the Hope (Tavernier Blue), the Regent (Pitt), the Orlov, the Nizam, and the Daria-i-Noor. Tavernier's Six Voyages (1676) provides the most detailed Western description of the workings as they functioned at their seventeenth-century peak, recording several thousand miners working open pits at Kollur and shipping rough downstream to Golconda for cutting and trade. Golconda itself was a famous fortress and trading entrepôt rather than a producing mine, but its name became a metonym in European usage for the diamonds of the entire region.

Decline

Production declined through the eighteenth century as the easily worked alluvials were exhausted. The discovery of Brazilian diamonds in Minas Gerais in 1725 shifted the world's centre of supply westward, and the later opening of the South African primary deposits in the 1860s and 1870s rendered the Krishna fields commercially marginal. By the late nineteenth century the workings had largely ceased, surviving only as artisanal operations.

Modern situation

The diamondiferous gravels are exhausted from a commercial standpoint. The kimberlite source bodies at Wajrakarur and the Anantapur tract have been investigated by the Geological Survey of India and various exploration ventures from the 1970s onward; small primary occurrences are documented but no significant economic deposit has been brought into production. The historical mines around Kollur are now archaeological sites, with limited preservation and intermittent academic study.

Trade legacy

For the modern trade, Golconda survives as a romantic descriptive term applied to old Indian diamonds of unusually high purity, particularly Type IIa stones lacking measurable nitrogen and showing exceptional transparency. The term has loose application: any stone of plausibly pre-South African Indian origin, with or without provenance documentation, is sometimes marketed as Golconda. Reputable laboratories will report diamond type (IIa, IaB and so on) but do not certify geographic origin for diamonds, so Golconda remains a trade descriptor rather than a verifiable claim.