Past and present ruby mines in Myanmar (Burma)

PAST AND PRESENT RUBY SOURCES OF MYANMAR

Mogok and Mai Hsu, Myanmar

Historically, Mogok, Myanmar, is the most important ruby source. The deposits there have produced rubies since the fifteenth century. The finest jewelry houses have used mogok rubies to create some of their most stunning pieces. These stones can possess the characteristics that most people treasure in a ruby-----vibrant red bodycolor, softened by the presence of light-scattering inclusions, and glowing with red fluorescence. Of course, not all stones from Mogok fit this description. Still, everyone wants a "Burmese" ruby.

The Mogok mining area is located about 60 mi. (100 km) northwest of Mandalay by air, and 300mi. (500 km) from Yangon. The area is very mountainous, much of it above 7,000 ft. (2,150m). The corundum deposits covers approximately 70 sq. mi. (175.km). Ruby is far more abundant at Mogok than sapphire. Some figures suggest that 90 percent of the yield is ruby, with only 10 percent of sapphire.

The rubies at Mogok are marble-hosted, and they're believed to have formed from a combination of contact and regional metamorphism. The rubies are recovered directly from the marble as well as from nearby river gravels. High annual rainfall causes rapid erosion and transport of the alluvial sediment. The rivers drain the area, carrying and concentrating the eroded materials across the valley floors. Most of the gemstones are mined from these alluvial sediments.

Mining activities are often suspended during the mid-May to mid-October rainy season. During the rest of the year, miners use various mechanized and primitive recovery processes. Although mining in Mogok is more efficient and organized than ever before, only small numbers of stones are recovered there today. The exact number is difficult to estimate since smuggling has long been a factor in Myanmar.  

Often considered to yield the finest color available, Mogok actually produces gems from pink sapphire to ruby. They can range from light, pale pinkish red through intense pinkish red, vibrant red, and very dark purplish red with medium to medium-dark tone and vivid saturation. They generally display strong to very strong fluorescence. Clarity characteristics typical to Mogok rubies are dense clouds of rutile silk and minute particles of other materials.

Today the majority of Mogok rubies are heat-treated for color enhancement. Because high temperatures dissolve the rutile silk that can actually improve the stone's appearance, a small percentage of the finest quality are left unheated. These stones, when accompanied by certificates that confirm the origin and the natural state, can command incredibly high prices.      

Myanmar has been the primary ruby source for centuries. But in the late 1960s, a coup upset the country's stability and the Mogok mines' production. Mines in Thailand began to supply bulk of rubies. In the early 1990s, as Thai supplies and those in nearby Cambodia became exhausted, Mai hsu, Myanmar gained status as an important source.

Mai hsu has supplied the world with the vast majority of its commercial-quality rubies since 1991. The Mai hsu mines are situated in Myanmar Shan State, which borders Thailand, Laos, and china, and is located 150 mi. (250 km) southeast of Mogok. Like the Mogok rubies, those at Mai hsu originated in marble deposits. Miners use mostly traditional small-scale methods to recover the rubies from deposits. Mai hsu crystals are rarely water-worn, which indicates that they weren't transported very far from their primary sources.

Mai shu ruby rough generally has a deeply saturated red color, but very few stones are a uniform red before treatment. Untreated rough typically has a dark core surround by a red rim. Heat treatment converts the core to red, making the red color uniform throughout the stone.

After treatment, rubies range from light pinkish to medium and dark red, purplish red and pinkish purple. Typical clarity characteristic that are believed to be a result of the treatment process include translucent zones of dense white clouds, finger print- like inclusions, and whitish hexagonal zoning related to the treatment of the core. Some treated stones might have glassy- appearing veils and feathers, which gives them the appearance of flux-grown synthetic rubies. The least expensive grades are often so included that they are translucent.

Heating might also produce highly reflective whitish zones in some stones. Further heat treatment can't remove this type of inclusions, so these rubies are unsuitable for polishing and have to be rejected.

Production from Myanmar is unstable. Civil unrest, political instability, and mining disaster have caused periodic decreases in production. Although Myanmar remains the world's major ruby source, it's difficult to predict the further when the nation's politics are so unpredictable.      


Christina