Since the fifteenth century the Mogok region of Myanmar has been producing some of the finest rubies. Following the instability in the country in the 1960s, production started to emerge from Cambodia and Thailand. However, when mines became depleted in these areas, Myanmar once again became the most important source.
The most superior Burmese rubies show a red to slightly ‘purplish’ hue, with vivid saturation and a medium-dark tone. The minute, light-scattering inclusions found in the stone are what create its characteristic softness.
The miniscule, parallel rutile needles that create silk clouds, along with the fingerprint inclusions and the tiny crystals of other minerals, are what create clarity in a ruby. Nowadays, most Mogok rubies are heat treated to dissolve the rutile silk and improve the stone’s appearance. The most desirable rubies are those that are left unheated – albeit only a small percentage.
Myanmar’s high-quality stones are formed around the irregularly dispersed layers of metamorphic rock such as marble. ‘Marble-hosted’ rubies have a pure red colour, due to the lack of iron present in the marble. The characteristic vibrant red of the Myanmar rubies is referred to as ‘pigeon’s blood’.
‘Marble-hosted’ rubies can be recovered from the marble in two ways: either directly from the marble itself or from the river gravels in the valley floors. Nowadays, the Mogok miners use a variety of techniques but only very small quantities of rubies are recovered.