Pelmadulla is a small town in the Sabaragamuwa Province of Sri Lanka, set in the lower foothills of the central highlands a short drive northeast of Ratnapura. The town's importance to the trade is geological rather than civic: it lies on the same network of alluvial gem gravels that has supplied corundum and chrysoberyl to the international market for more than two thousand years. Mining is by traditional pit methods, and the town functions as a local market for rough material that ultimately moves through Ratnapura and Colombo to cutting centres in Bangkok, Hong Kong, and Jaipur.

Geological setting

The Sabaragamuwa gravels are secondary deposits — sediments eroded from the underlying high-grade metamorphic basement of the Highland Complex and concentrated by river systems into broad alluvial flats. The gem-bearing horizon, called illam in Sinhalese, is typically a layer of poorly sorted gravel one to several metres thick, lying beneath barren overburden of clay and topsoil. Illam contains a polymineral assemblage: sapphire and ruby, chrysoberyl and cat's eye, spinel, garnet, zircon, topaz, tourmaline, and a long tail of minor species. Pelmadulla sits well within this gem-bearing province.

Production

The corundum from Pelmadulla and the surrounding district covers the full Sri Lankan range: blue sapphire in tones from pale Ceylon blue to deep velvety navy, fancy yellow and pink sapphire, padparadscha in the rare cases where pinkish-orange material is recovered, and star sapphire from rutile-included rough. Chrysoberyl is the second pillar of the local production, with both faceted yellow-green stones and the prized cat's eye phenomenon present in the gravels. Star and cat's eye material is often recovered as waterworn pebbles already showing the silk that will produce the phenomenon after orientation and cabbing.

Mining method

Sabaragamuwa mining is dominated by small-scale operations using methods that have changed little since the colonial period. A team of five to ten men sinks a vertical shaft, often less than a metre square in cross-section, through overburden until the illam horizon is reached. The gravel is hauled up by hand, washed in a bamboo basket called a ketta in the nearest stream, and concentrated by skilled rocking. Heavy minerals settle to the centre of the basket and are inspected by eye. Mechanised mining is restricted by Sri Lankan law to specific licensed operations, and the small-scale model has the secondary effect of distributing income broadly through the local economy.

In the trade

Material from Pelmadulla is rarely sold under the town name. By the time rough reaches a cutter or a buyer, the geographic descriptor has compressed to Ceylon or Sri Lanka, and origin reports from Gübelin, SSEF, and GIA make the same broad attribution. The Sabaragamuwa origin is reflected in trace-element fingerprints — high iron with low titanium for some blue sapphire, distinctive vanadium content for some colour-change material — but the laboratories do not subdivide Sri Lankan deposits at the town level. For collectors and dealers, the more useful provenance frame is the broader Ratnapura district, of which Pelmadulla is one productive corner.

Further reading

• GIA Gems & Gemology — Sri Lankan corundum localities
• ICA — Sri Lanka sapphire mining
• Lotus Gemology — Ceylon sapphire and origin
• International Gem Society — Sri Lankan gem deposits