Mineral Inclusions in Ruby and Sapphire from the Bo Welu Gem Deposit in Chanthaburi, Thailand

Thailand are located in the provinces of Chanthaburi-Trat, Kanchanaburi, PhraeSukhothai, Ubon Ratchathani, Si Sa Ket, and Phetchabun (figure 1). However, a few main areas have been economically mined and supplied gems to the world market. Sapphire mines were once extensively operated in Kanchanaburi, but most have recently closed down. The Chanthaburi-Trat area has been the most significant source of Thai corundum, and a few small mines are still in operation there. The most famous source of Thai rubies is located in the Bo Rai deposit in the eastern part of Trat Province, close to the Cambodian province of Pailin (figure 1). What became known as “Siamese ruby” was first named from here and adjacent areas. Meanwhile, the main gem mining area for sapphire (yellow, green, and blue, along with golden star and black star sapphires) is the Bang Ka Cha deposit in western Chanthaburi (again, see figure 1). Most gem mines in the central deposits, around Khlung District within Chanthaburi Province, have supplied more sapphire than ruby (Vichit, 1992; Pattamalai, 2015). The focus of this study, the Bo Welu gem field located in the central gem deposits, has been mined for both ruby and sapphire. Corundum from this area is generally heat-treated to enhance its color, especially the red (or purplish red) ruby and the blue sapphire (figure 2), which are in high demand, particularly within Thailand.