Beryl

At least 50 different beryllium-bearing minerals are known, but in only about 30 is it a regular constituent. The only beryllium-bearing mineral of industrial importance is beryl, a hexagonal beryllium-aluminum silicate with the ideal composition Be3Al2Si6O18, equivalent to 5% beryllium or 14% beryllium oxide, 19% A12O3, and 67% SiO2. The precious forms of beryl, emerald and aquamarine, approach the ideal composition. The emerald is a transparent, intensely green variety of beryl.