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

Abstract

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.Although gem mines in this area are not currently in operation, a few artisanal miners can be found working along streams during the rainy season. The rarity of Thai ruby ensures strong demand in the local and international markets and high value. The sapphires, meanwhile, possess a natural greenish blue color that becomes an intense blue after heating.In this study, ruby and sapphire from Bo Welu were investigated to determine their mineral inclu-

Mineral Inclusions in Sapphire from Basaltic Terranes in Southern Vietnam: Indicator of Formation Model

“…This magmatism should have taken place extensively prior to fractionated crystallization in the lower crust. This model agrees well with the genetic model proposed by Aspen et al (1990), Sutherland et al (1998a, 2009, Pin et al (2006), Zaw et al (2006), Upton et al (2009), Khamloet et al (2014), and Promwongnan and Sutthirat (2019).…”

“…On the other hand, these zircon inclusions yielded Th/U ratios >0.2, indicating a magmatic source (Williams and Claesson, 1987;Rubatto and Gebauer, 2000;Huong et al, 2016). These were similar in composition to zircon analyses previously reported from Dak Nong (Izokh et al, 2010) and other basalt-associated sources such as Ban Huai Sai in Laos, Kanchanaburi in Thailand, and Kings Plains and New England in Australia (Guo et al, 1996;Sutherland et al, 1998a;Khamloet et al, 2014), although the Y 2 O 3 content of zircon inclusions from Bo Welu in Thailand (Promwongnan and Sutthirat, 2019) has recently been reported with a higher content. Total REE contents of representative zircon inclusions ranged from 1156 to 2710 ppm (table 4), more similar to those from syenite pegmatite (2043 ppm) and granitoid (1813 ppm) than those from carbonatite (600-700 ppm) (Belousova et al, 2002).…”

“…It has been suggested that sapphire and ruby deposited within basaltic terranes could not have crystallized directly from basaltic magma (Coenraads, 1992;Levinson and Cook, 1994;Guo et al, 1996;Sutherland et al, 1998aSutherland et al, , 2002Sutherland et al, , 2015Khamloet et al, 2014;Promwongnan and Sutthirat, 2019). A corroded surface is a typical feature observed in basalt-associated sapphires, clearly indicating transport by the hot magma.…”

“…They were often associated with zircon, with or without feldspar (figures 7C and 9B). Representative EPMA analyses of columbite inclusions Izokh et al (2010), using EPMA b Long et al (2004), using SEM-EDS c Smith et al (1995), using SEM-EDS d Promwongnan and Sutthirat (2019), using Raman and EPMA e Saminpanya and Sutherland (2011), using EPMA f Khamloet et al (2014), using EPMA g Sutherland et al (1998b), using EPMA h Sutherland et al (2002), using EPMA i Palke et al (2019) 8). Their compositions were also equivalent to those previously reported for sapphires from Dak Nong by Izokh et al (2010) as well as from Lava Plains and New England in Australia (Guo et al, 1996;Sutherland et al, 1998b).…”

Intriguing minerals: corundum in the world of rubies and sapphires with special attention to Macedonian rubies

“…Inclusions in rubies and sapphires are extremely important, and typically described separately for each location, as presented for the Bo Welu gem deposit in Chanthaburi, Thailand [26]. In general, the most significant inclusions in rubies and sapphires are silk (Fig.…”