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Mineral, BeAl2O4; sp. gr. 3.5–3.8; hardness 8.5; orthorhombic; various shades of green or greenish-yellow; white streak; vitreous lustre; crystal form tabular; cleavage prismatic {110}; occurs in granites, pegmatites, and mica schists, also in alluvial sands and gravels. The emerald-green variety is used as a gemstone (alexandrite).

Subjects: Earth Sciences and Geography.

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