Thailand is known for producing rubies with high clarity and a deep red “Siamese” color. As early as the 15th century, visitors forwarded glowing reports of the fabulous rubies that could be found there. In 1687, the French envoy to Siam reported that the country was “abounding in mines of rubies and sapphires.” He also noted that the local Thai farmers used these gemstones as amulets and talismans.
Although rubies were known to exist in Thailand for centuries, they were not extensively mined until relatively recently. In 1895, the rights to mine in Siam were granted to a British company called The Sapphires and Rubies of Siam, Ltd. This company was related to The Burma Ruby Mines Ltd., which worked the famous mines of the Mogôk Valley in Myanmar.
Unfortunately, the Thai venture was not commercially successful. Since 1919, when the Siam Mining Act was passed, gem extraction in the country has been reserved for Thai nationals. Declining production in other countries and improved heat treatment methodologies made Thai rubies more desirable after the 1960s.
In fact, by the mid 1980s, Thai deposits accounted for about 80 percent of the world’s ruby supply. Thai rubies tend to be darker than rubies from other countries, but heat treatments can eliminate the common, but undesirable, brown and bluish tones. Thai rubies are also known for their clarity and absence of silk.
A majority of Thailand’s rubies have been produced at the Chanthaburi mines in the southeastern corner of the country. There, rubies are found in alluvial deposits of weathered alkali-basalts, which accounts for their high iron content and lack of fluorescence .
Although Thai deposits are now depleted, the country has maintained its position as a focal point of the world’s ruby industry. Both Bangkok and Chanthaburi have become major ruby cutting, treatment, and marketing centers, drawing an international clientele. As the ruby market in Cambodia heats up, many seasoned miners and Thai mining companies are moving into the neighboring country to continue the search for rubies.
Continuing on our discovery of top ruby mining regions of the world, we visit another neighbor in Asia in our guide to Ruby Mining in Cambodia.