The authors recently examined the 2.52 ct saturated green oval modified brilliant shown in figure 1. The gemological properties, as well as trace element analysis using laser ablation–inductively coupled plasma–mass spectrometry, confirmed this gem was a Paraíba tourmaline from Brazil.
Microscopic observation revealed interesting metallic dark gray dendritic inclusions (figure 2). The metallic inclusions were similar in shape to previously documented native copper inclusions in Paraíba tourmaline (E.J. Gübelin and J.I. Koivula, Photoatlas of Inclusions in Gemstones, Volume 1, 2008, Opinio-Verlag Publishers, Basel, Switzerland, p. 167). Metallic inclusions with a dendritic pattern and similar brassy color in a Brazilian Paraíba tourmaline were previously identified as native copper (F. Brandstätter and G. Niedermayr, “Copper and tenorite inclusions in cuprian-elbaite tourmaline from Paraíba, Brazil,” Fall 1994 G&G, p. 181). Because the inclusions in figure 2 are different in color from those previously documented, they are probably not copper. However, Raman analysis was unsuccessful in identifying them. Based on their morphology and color, the authors speculate they could be ilmenite, which has been observed as skeletal inclusions of a similar color in gems such as emerald. These are the first examples of dark gray skeletal metallic inclusions the authors have encountered in a Paraíba tourmaline.
Shiva Sohrabi is a staff gemologist, and Amy Cooper is supervisor of colored stone identification, at GIA in Carlsbad, California.
The authors recently examined the 2.52 ct saturated green oval modified brilliant shown in figure 1. The gemological properties, as well as trace element analysis using laser ablation–inductively coupled plasma–mass spectrometry, confirmed this gem was a Paraíba tourmaline from Brazil.
Microscopic observation revealed interesting metallic dark gray dendritic inclusions (figure 2). The metallic inclusions were similar in shape to previously documented native copper inclusions in Paraíba tourmaline (E.J. Gübelin and J.I. Koivula, Photoatlas of Inclusions in Gemstones, Volume 1, 2008, Opinio-Verlag Publishers, Basel, Switzerland, p. 167). Metallic inclusions with a dendritic pattern and similar brassy color in a Brazilian Paraíba tourmaline were previously identified as native copper (F. Brandstätter and G. Niedermayr, “Copper and tenorite inclusions in cuprian-elbaite tourmaline from Paraíba, Brazil,” Fall 1994 G&G, p. 181). Because the inclusions in figure 2 are different in color from those previously documented, they are probably not copper. However, Raman analysis was unsuccessful in identifying them. Based on their morphology and color, the authors speculate they could be ilmenite, which has been observed as skeletal inclusions of a similar color in gems such as emerald. These are the first examples of dark gray skeletal metallic inclusions the authors have encountered in a Paraíba tourmaline.
Shiva Sohrabi is a staff gemologist, and Amy Cooper is supervisor of colored stone identification, at GIA in Carlsbad, California.
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