The Mogok region of Myanmar (previously Burma) is the most important source of rubies and has been producing some of the finest of these gems since the fifteenth century.
Myanmar mining production was disrupted in the late 1960s when the government was overthrown, unsettling the country’s stability. Following this disruption, production started to come from Thailand and Cambodia, but as their mines became exhausted Myanmar became known as the most important ruby source once again.
The most renowned rubies use the term ‘Burmese’ to indicate the high quality, regardless of their origin. The finest Burmese rubies display a red to slightly 'purplish' hue, with vivid saturation and a medium-dark tone. The characteristic softness often displayed in rubies comes from them having minute, light-scattering inclusions.
The clarity characteristics are often created from minuscule rutile needles creating silk clouds, fingerprint inclusions and tiny crystals of other minerals. Many of Mogok's rubies are now heat treated to dissolve the rutile silk thus improving the stone's appearance, although a very small percentage of the highest quality rubies are left unheated – these are particularly desirable.
Myanmar's high-quality, vibrant red ‘pigeon's blood’ stones are typically formed in metamorphic rocks such as marble. They are found when the layers have been irregularly dispersed within the surrounding marble. Due to marble having such a small amount of iron present ‘marble-hosted’ rubies lack iron, giving them their pure red colour, and allowing their characteristic fluorescence to display.
‘Marble-hosted’ rubies can be recovered in two ways, either directly from the marble or from the nearby river gravels. The high annual rainfall that is experienced in the Mogok region causes the quick erosion of the rock and transports it to the river bed sediment. The rivers then drain the area leaving the river gravels concentrated in the valley floors from which the stones can then be mined. Today, the miners in Mogok use a variety of techniques to source the stones that have been developed and refined over centuries; however, only very small quantities of fine gemstones are recovered from the processes.