Commercially important quantities of gem-quality sapphire, spinel, garnet, chrysoberyl, zircon, tourmaline, and many other gemstones are being recovered from deep gem pits and surface excavations in the Elahera gem field, a region in central Sri Lanka about 115 km northeast of the capital city of Colombo. Large-scale mining is being conducted in this highly metamorphosed sedimentary deposit by the State Gem Corporation in collaboration with the private sector. The chemistry and gemological characteristics of these gem materials are discussed; in many instances, characteristic inclusions were identified by microscopy, microprobe analysis, and X-ray powder diffraction analysis. It is estimated that the Elahera gem field currently provides approximately 35% of the gemstones exported from Sri Lanka. The continued steady production of good-quality gems is anticipated for the future.
