Micro-World Gems & Gemology, Fall 2019, Vol. 55, No. 3

Dravite from Mozambique with an Abundance of Pyrite Inclusions

Weizhi Huang and Jingcheng Pei

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Dravite tourmalines from Mozambique featuring pyrite inclusions.
Figure 1. Six yellow to brownish yellow faceted dravite tourmalines (0.47–2.8 ct) from Mozambique, many of which contained distinct metallic inclusions of pyrite. Photo by Weizhi Huang.

In the summer of 2017, author JP encountered a parcel of transparent yellow to brownish yellow tourmalines at the gemstone market in Chanthaburi, Thailand. The six faceted tourmalines shown in figure 1 revealed properties consistent with tourmaline. LA-ICP-MS analysis was performed to determine their major chemical components, which were: 11.56–12.31% MgO, 9.98–10.34% B2O3, 2.62–2.82% Na2O, 0.68–1.06% CaO, 0.17–0.45% TiO2, and 0.11–0.25% FeO (total iron). Minor amounts of Li, K, V, Cr, Mn, Zn, Ga, and Sr were also detected, indicating dravite tourmaline.

Euhedral pyrite crystal inclusions confirmed by Raman spectrometry.
Figure 2. The dravites contained distinctive inclusions of pyrite, which were confirmed by Raman spectrometry. Photomicrograph by Weizhi Huang; field of view 0.8 mm.

These dravites were noteworthy for their numerous euhedral pyrite crystal inclusions (figure 2), confirmed by Raman. This was previously reported without Raman analysis (see Spring 2007 GNI, pp. 73–75). This is the first time the authors have seen so many intact pyrite crystals in yellow to brownish yellow gem-quality dravite from Mozambique.

Weizhi Huang and Jingcheng Pei are affiliated with the Gemmological Institute, China University of Geosciences, in Wuhan.