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Formula:   Be3Al2(Si6O18)   mineral photo

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Crystal:   Hexagonal  
Hardness:   7.5-8  
Spec. Gr.:   2.66-2.83  
Streak:   White  
Cleavage:   Imperfect basal  
Location:   Carnaiba, Campo Formoso, Bahia, Brazil  

The Carnaiba mining district lies about 27km southwest of Campo Formoso, and is 77km north of Jacobina in the Brazilian state of Bahia. Here yields emeralds of only fair gem quality, but some of good crystal forms are found. The emeralds are found in ROCHA VERDE or green rock (chromium bearing) outcrops, which in turn are in decomposed granite rocks and vermiculite-biotite schists. The largest emerald discoveries were made in 1969 when about 6000 persons rushed to the area, including dependents and camp followers. These deposits are defunct at present. Emerald is the green member of the beryl family. It occurs as greenish six-sided prismatic crystals with a hardness of 7.5-8, sufficient for use in jewelry. Other localities are in Egypt, India, Russia, Columbia, and North Carolina, among others.

Bibliography: Alain, Eid, Minerals of the World, pg. 51.

Sinkankas, John, Emeralds and Other Beryls, 1981, pg. 383-386.

University of California, Santa Barbara—Department of Earth Science
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