Chrysoberyl is a mixed oxide mineral of beryllium and aluminum (BeAl2O4).
It is found in beryllium-rich pegmatite dikes; Brazil is a leading source. Its hard,
hexagonal system crystals are prismatic or tabular. It can be transparent,
green, yellow, or brown, but bright yellow-green is most highly valued.
Alexandrite and cat's eye are gem varieties. Hardness 8.5, relative density 3.69.
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