Crysoberyl
Crysoberyl is a beryllium aluminum oxide, which produces the
gemstones alexandrite and cat's - eye. It's tabular
crystals (orthorhombic system) are transparent to
translucent, yellowish green to green or brown, and have
a vitreous luster. Common chrysoberyl occurs as crystals
or loose, rounded grains in granitic pegmatites, and in
metamorphic rocks such as schist and gneiss.