Rubies & Sapphires of Thailand and Cambodia: Information

Important sources for rubies and sapphires exist in Thailand and Cambodia. The ruby deposits occur along the Thai/Cambodia border in hanthaburi and Trat province in Thailand, and neighbouring Battambang rovince in Cambodia. The rubies tend to be brownish red and somewhat dark in colour, while the sapphires are generally dark blue. Fine yellow sapphires occur at Khao Ploi Waen and Bang Ka Cha, while blue sapphires occur mainly at Khao Ploi Waen, Bang Ka Cha and Bo Ram in Thailandand Pailin in Cambodia. Rubies are found in a wide area including Bo Rai, Nong Bon, Bo Waen and Tok Prom in Thailand and Pailin in Cambodia. The centre for the gem trade in this area is the Thai town of Chanthaburi.
All gem deposits in this area are derived from iron-rich basalt. The high iron content of the mother rock carries over into the corundum, which is generally darker than the ideal. The stones are found in coarse yellow or brown sand, overlaying a bed of clay or basaltic rock. The beds are mostly within 2.5 m of the surface, but some of the mines are over 6 m deep. These deposits have only been worked to any extent since the late nineteenth century. Mining is by simple methods. Blue sapphires are also found in western Thailand at the town of Bo Ploi, in Kanchanaburi province. In the late 1980s mining at Bo Ploi was expanded dramatically, but has since declined.