Trapiche rubies are composed of six translucent-to-transparent ruby sections that are delineated by “arms” of translucent-to-opaque material, resulting in a fixed six-rayed “star.” Such rubies have been reported from both Mong Hsu, Myanmar (see K. Schmetzer et al., Winter 1996 Gems & Gemology, pp. 242–250; Summer 2000 Gem News, pp. 168–169; and V. Garnier et al., “Rubis trapiches de Mong Hsu, Myanmar,” Revue de Gemmologie, No. 144, 2002, pp. 5–12) and Yen Bai Province, Vietnam (see Fall 1998 Gem News, p. 225). The arms in the Mong Hsu material reportedly consist of ruby and solid, liquid, and two-phase inclusions, with the solid inclusions composed of calcite and dolomite; micas reportedly form the “star” in the Vietnamese material.

At the Pueblo Inn during the February 2003 Tucson shows, David Burton of Burton’s Gems & Opals, Anaheim, California, had five heat-treated cabochons of trapiche ruby that also showed asterism. According to Mr. Burton, such material has been found only in Mong Hsu. We examined a 0.49 ct sample (see figure) that was acquired by one of these contributors (EQ). It had a spot R.I. of 1.77 and a specific gravity (measured hydrostatically) of 3.86; the latter is slightly lower than the values previously reported for trapiche rubies. The sample displayed a typical ruby (chromium) absorption spectrum when viewed with a desk-model spectroscope. It fluoresced moderate to strong red to long-wave and weak chalky red to short-wave UV radiation. Viewing the sample with magnification and a UV lamp revealed that the fixed arms fluoresced a very weak chalky yellow to long-wave UV only. (However, this effect was nearly overpowered by the fluorescence of the surrounding ruby.) Magnification also revealed fine silk, hexagonal growth zoning, numerous fingerprints, growth tubes, and cavities.

EDXRF analysis of one of the ruby sections revealed traces of K, Ca, Ti, V, Cr, Fe, and Ga. Another analysis of the top of the dome where the arms of the fixed star came together showed significantly more Ca and Ti, and less K and Fe, than the ruby section. The bottom of the sample (the only part tested in this way) effervesced slowly to 10% HCl, mainly along the fixed arms, indicating the presence of a carbonate mineral. Unfortunately, it was not possible to confirm the identity of the mineral(s) in those arms by Raman spectroscopy, due to the strong fluorescence of the sample.

The two stars in this asteriated trapiche ruby were created independently by different types of inclusions. It has been suggested (in the above-referenced articles) that the fixed arms of the Mong Hsu trapiche rubies are primary inclusions. The asterism is created by fine silk, however, which is secondary and crystallizes as the corundum cools.