Since 1993, large amounts of gem-quality sapphires from the Andranondambo region of southern Madagascar have entered the international gem market. These sapphires, which are found in metamorphic skarn-type deposits, show a broad range of gemological and chemical properties, many of which are similar to those of sapphires from Sri Lanka, Myanmar (Burma), and even Kashmir. Most of the Andranondambo sapphires are heat treated in Bangkok; these can be separated from their non-heat-treated counterparts on the basis of inclusion features and absorption spectra. Key factors in the separation of Andranondambo sapphires from synthetic sapphires of different manufacturers are chemistry (especially the Ga content of the natural material) and internal features.
