Beryl

Beryl, mineral and, in certain varieties, a valuable gem material. Chemically it consists of aluminum beryllium silicate, Be₃Al₂(SiO ₃)₆, and it is the chief commercial ore of beryllium. Pure beryl is colorless and transparent. Emerald, one of the most valuable gems, is a variety that is colored green by minute amounts of chromium. Aquamarine, also a gemstone, is a blue beryl, more common than emerald. Golden beryl and morganite or rose beryl are less valuable. Colorless beryl is occasionally used as a gem under the name goshenite. Beryl has a vitreous luster with little fire or brilliancy, and so its value depends principally on hardness, transparency, and color. It has a hardness of 7.5 to 8 and a specific gravity of 2.75 to 2.8.

Beryl crystallizes in the hexagonal system. Large lettuce-green opaque crystals, some weighing over a ton, are found embedded in a variety of granite called pegmatite. Large, transparent crystals of the colored varieties are occasionally found.