Beryl is beryllium silicate, Be3Al2Si6O18. A ring silicate, it is also a gemstone under various names including emerald, aquamarine and morganite. (more below)
Beryl is commonly found in pegmatites and is usually in well-formed crystals like this hexagonal prism. Its hardness is 8 on the Mohs scale
, and it usually has the flat termination of this example. Flawless crystals are gemstones, but well-formed crystals are common at rock shops. Beryl can be clear as well as various colors. Clear beryl is sometimes called goshenite, the bluish variety is aquamarine, red beryl may sometimes be called bixbyite, green beryl is better known as emerald, yellow/yellow-green beryl is heliodor, and pink beryl is known as morganite.
Other Metamorphic Minerals