Gem-quality blue to bluish green sapphires from basaltic terrains in southern provinces of Vietnam have been entering the gemstone market since the late 1980s.Visits to two of the sapphire-producing areas—Phan Thiet and Di Linh—confirmed that the sapphires occur in association with alkali basalts. Mining was done by hand at the Phan Thiet localities and with relatively sophisticated equipment at Di Linh. Investigation of 250 faceted samples revealed gemological, spectroscopic, and chemical properties similar to those of other basaltic sapphires. Notable internal features are prominent growth structures, distinctive color zoning, various crosshatch to lath-like "cloud" patterns, and several mineral inclusions.
Gem-quality blue to bluish green sapphires from basaltic terrains in southern provinces of Vietnam have been entering the gemstone market since the late 1980s.Visits to two of the sapphire-producing areas—Phan Thiet and Di Linh—confirmed that the sapphires occur in association with alkali basalts. Mining was done by hand at the Phan Thiet localities and with relatively sophisticated equipment at Di Linh. Investigation of 250 faceted samples revealed gemological, spectroscopic, and chemical properties similar to those of other basaltic sapphires. Notable internal features are prominent growth structures, distinctive color zoning, various crosshatch to lath-like "cloud" patterns, and several mineral inclusions.
