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This 9.50 ct. euclase from the Chivor emerald mine in Colombia is notable for its size and intense greenish blue color. Photo by C. D. Mengason.
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Recently, some fine gem-quality crystals of blue euclase have been appearing in the Colombian market, and the faceted gems are sometimes seen in parcels of cut emeralds offered in Bogotá. The cut euclase is light-to-medium greenish blue, and the stones typically weigh less than 2 ct. By contrast, the 9.50 ct. Chivor euclase shown here is notable for its size and intense greenish blue color; the rough was reportedly mined in 2005.
This 9.50 ct. euclase was loaned to the GIA Laboratory for examination, and the following gemological properties were recorded by Shane F. McClure: Color – greenish blue; pleochroism – near colorless, light purple, and blue-green; R.I. – 1.650–1.670; biaxial optic figure; hydrostatic S.G. – 3.10; fluorescence – inert to long- and short-wave UV radiation; and no spectrum was observed with the desk-model spectroscope. Examination with a gemological microscope revealed a large cleavage plane, inclusions of tiny transparent colorless crystals, and strong angular graining and associated color zoning.
The Spring 2003 Lab Notes section reported on an attractive crystal specimen of greenish blue euclase from Pauna, Boyacá District, Colombia (also see Spring 2004 Gems & Gemology, p. 65). Another Colombian source for blue euclase is the famous Chivor emerald mine, also located in the Boyacá District. The euclase was initially found in the 1980s, when a large amount of emeralds were produced from Chivor. The miners paid little attention to the euclase because they lacked knowledge of the material and were focused on the important emerald production at that time.
In addition to Colombia, gem-quality euclase is known from Brazil and Zimbabwe (Summer 1993 Lab Notes, pp. 125–126).
Daniel A. Sauer (Amsterdam Sauer, Rio de Janeiro) and Brendan M. Laurs.
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