Feature Gems & Gemology, Summer 2012, Volume 48, No. 2

Sapphires from Thammannawa, Kataragama Area, Sri Lanka

Pannipitiye G. R. Dharmaratne, H. M. Ranjith Premasiri, and Dayananda Dillimuni

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The February 2012 discovery of high-quality blue sapphires at Thammannawa near Kataragama in southeastern Sri Lanka has intensified gem mining and exploration in the surrounding area and all over the country. The deposit is hosted by the Kataragama klippe, and corundum mineralization is associated with pegmatitic intrusions and surrounding micaceous layers. Well-formed crystals from this primary deposit display flat faces and sharp edges with an unusually vitreous luster. The sapphires possess good transparency and a pure blue color that is characteristic of corundum from this deposit. Several kilograms of rough material have been produced so far, with some crystals larger than 200 g. Faceted blue sapphires of fine color and weighing more than 20 ct have been cut.