The mineral beryl (also Beryllium aluminium meta-silicate and Beryllium aluminum meta-silicate) is a silicate of beryllium and aluminium with the chemical formula Be3Al2(SiO3)6. It has a vitreous lustre and can be transparent or translucent. Pure beryl is colorless, but it is frequently tinted by impurities; possible colors are green, blue, yellow, red, and white.
Beryl has been considered a gemstone since prehistoric times. Green beryl is called emerald, red beryl is bixbite or red emerald or scarlet emerald, blue beryl is aquamarine, pink beryl is morganite, and a clear bright yellow beryl is called golden beryl or heliodor. Other shades such as yellow-green and honey yellow are common.
Beryl has a hardness between 7½ and 8. It is somewhat brittle making it vulnerable when used as a ring stone. When cut in cabochon form it is generally more durable than faceted stones. Emerald is especially subject to fracture due to its inclusions. The emerald cut was developed to overcome this problem. Pliny observed that beryl often occurs in six-sided prism. He goes on to state that the Hindus often drilled out these natural prisms to make beaded jewelry.