jade, jadeite, fei cui, Burma, maw-sit-sit, gems, Broken Bangle

Progress in the Gemological Institute of America’s research program is reviewed, with particular attention to a revised identification of the constituents of maw-sit-sit, the mottled green ornamental material from Myanmar. The broader program centers on establishing a reference collection and documenting the properties of its more than 9,000 cataloged specimens. Research priorities include the origin of color in diamond and lavender fei cui, the classification of gem garnets, color permanence, and the major- and minor-element composition of gem materials. Maw-sit-sit, first described in the 1950s, is investigated using scanning electron microscopy, energy-dispersive X-ray chemical analysis and powder X-ray diffraction of finely ground mineral separates. The report attributes earlier difficulties in identifying its constituents to their intimate intergrowth and to the limitations of analytical methods previously available. The dark green, almost black component, formerly described as chromium-bearing jadeite, is identified as the pyroxene then called ureyite. Manson notes that this mineral had previously been recognized in meteorites and presents its identification in maw-sit-sit as a terrestrial occurrence. The intimately associated colorless to white component, previously regarded as albite feldspar, is reported to be natrolite on the evidence of clean separates. These findings are presented as corrections to earlier descriptions of this jade-like aggregate. Another research result concerns a gem-quality hexagonal crystal discovered among spinels from Mogok, Myanmar. Measuring approximately 7.5 mm long and 3 mm across and weighing 1.7 ct, it is identified by X-ray methods and other properties as the second known painite specimen. Its reported lack of zirconium prompts comparison with the type material and a reassessment of the mineral’s initially proposed composition. The report also introduces investigations of unusual East African garnets against a background of complex metamorphic history and widespread trace vanadium. A rich golden-orange garnet with refractive indices of 1.74–1.76 and a strong manganese spectrum illustrates the difficulty of accommodating all newly encountered materials within established gemological varieties.