Micro-World Gems & Gemology, Summer 2019, Vol. 55, No. 2

Intergrown Emerald Specimen from Chivor

Luis Gabriel Angarita, John Jairo Zamora, and Jonathan Muyal

Emerald inclusion inside a large emerald specimen.
Figure 1. An emerald crystal inclusion measuring ~2.67 × 2.71 × 5.43 mm is found inside this large emerald specimen (18.35 × 10.69 × 9.79 mm) from Colombia’s Chivor mine. Photo by John Jairo Zamora.

Colombia’s Chivor emerald mines are located in the eastern zone of the Eastern Cordillera range of the Andes Mountains. Chivor translates to “green and rich land” in Chibcha, the language of the indigenous people who were already mining emerald more than 500 years ago, before the arrival of the Spanish conquistadors (D. Fortaleché et al., “The Colombian emerald industry: Winds of change,” Fall 2017 G&G, pp. 332–358). Chivor emeralds exhibit a bright green color with a tint of blue; they have relatively high clarity and fewer inclusions than emeralds found in Colombia’s western belt.

The authors recently examined a rough emerald crystal specimen (figure 1), measuring 18.35 × 10.69 × 9.79 mm, reportedly from Chivor. This crystal weighed 3.22 g (16.10 ct) and had a prismatic hexagonal crystal shape. Standard gemological examination confirmed the gemstone to be emerald, and ultraviolet/visible/near-infrared (UV-Vis-NIR) spectroscopy showed a classic Colombian emerald absorption spectrum. The crystal’s color was typical of Chivor emeralds, a medium dark green showing a blue tint. The emerald, which hosted jagged three-phase inclusions that are typically observed in Colombian material, showed no signs of clarity enhancement.

Well-formed emerald inclusion in a hexagonal shape (left and right).
 
 
 
Figure 2. Left: A well-formed emerald inclusion, showing a hexagonal prismatic shape with pyramidal termination. Right: The view from below shows a perfect hexagonal crystal outline. Photomicrographs by John Jairo Zamora; field of view 12 mm.

The emerald specimen hosted a large, unique inclusion of emerald almost perpendicular to the c-axis, measuring approximately 2.67 × 2.71 × 5.43 mm. The inclusion’s identity was confirmed by Raman spectroscopy. The inclusion exhibited a well-formed hexagonal prismatic shape with pyramid-like termination (figure 2). Although intergrowth emerald crystals have been described and documented in the literature several times (G. Grundmann and G. Giuliani, “Emeralds of the world,” in G. Giuliani et al., Eds., Emeralds of the World, extraLapis English, No. 2, 2002, pp. 24–35; I. Sunagawa, Crystals: Growth, Morphology and Perfection, Cambridge University Press, 2005, pp. 127–149), it is always a spectacular feature to observe, making this emerald rough crystal from Chivor with an emerald crystal inclusion a unique collector’s specimen.

Luis Gabriel Angarita is director, and John Jairo Zamora is a gemologist, at CDTEC Gemlab in Bogotá. Jonathan Muyal is a staff gemologist at GIA in Carlsbad, California.