Micro-World Gems & Gemology, Winter 2017, Vol. 53, No. 4

Complex Yellow Fluid Inclusions in Red Burmese Spinel

Negative crystal in Burmese red spinel.
This octahedral-shaped negative crystal in a Burmese red spinel is filled with colorless carbonate crystals, yellow sulfur-rich liquid, opaque sulfide crystals, and diaspore fibers. Photomicrograph by Victoria Raynaud; field of view 1.20 mm.

Spinel has found new popularity and is now recognized as a birthstone for August. Some of the most desirable stones come from Myanmar, as they exhibit a pure red color with a light tone, accompanied by extremely high fluorescence under long-wave UV. Red Burmese spinel can also be found with a dark tone and much weaker fluorescence. The main localities that produce the highly fluorescent spinel are Namya in northern Myanmar and Man Sin in the Mogok Valley (V. Pardieu, “Hunting for ‘Jedi’ spinels in Mogok,”Spring 2014 G&G, pp. 46–57). Clean stones are rare, as the majority have inclusions consisting of colorless carbonate crystals and complex multiphase negative crystals. These complex negative crystals contain a sulfur-rich yellow liquid, opaque metal sulfides, transparent carbonate daughter crystals, diaspore fibers, and a gas bubble. This unique yellow complex fluid inclusion (see above) is only known to occur in Burmese spinel and therefore serves as a good indicator of this origin.

Wim Vertriest is supervisor of field gemology at GIA in Bangkok. Victoria Raynaud is affiliated with the Bahrain Institute of Pearls and Gemstones (DANAT), based in Manama.