Beryl is the mineralogical term applied to Emerald, Aquamarine and four other gems. They are chemically and structurally identical to each other and are treated as a single group under this term. Beryl is a relatively common mineral and comes in a variety of colors from various different locations around the world. Beryl is best known for its Emerald variety and pale blue-green type known as Aquamarine.
 

The name Beryl is from the Ancient Greek “Beryllos” for the precious blue-green color of sea water. This was originally applied to all green gemstones, but later used only for Beryl. Some scholars believe the world Beryl is related to the ancient trading city of Belur or perhaps come from the world pearl known as “Velurya” in old Hindi and “Vaidurya” in Sanskrit.
 

Beryl is, when absolutely pure, totally devoid of color. Small amounts of metallic elements can be present in the crystal structure, giving rise to many color variations. Beryl comes in a wide range of colors and can also exhibit differing phenomena. All transparent Beryl varieties are used as gemstones.
 

Gemstone color varieties that belong to Beryl with specific names are listed below. All other colors of Beryl being simply referred to by their color (i.e. Golden Beryl):
 

Beryl is famous for their perfect, six-sided prismatic hexagon crystals that usually occur individually. These are often enormous and some 30-foot (8 meter), well-crystallized examples are known to have existed.
 

All Beryl varieties can be faceted into various gem cuts, and some Beryls display phenomena including Asterism (also known as the Star Effect this is a reflection effect that appears as two or more intersecting bands of light across the surface of a gem), Chatoyancy (also known as the Cat’s Eye Effect this is a reflection effect that appears as a single bright band of light across the surface of a gemstone) and an unusual effect in Emerald called Trapichism (these are star-shaped rays that emanate from the center of gem in a hexagonal pattern. These rays appear much like Asterism, but unlike Asterism, they are not caused by light reflection from tiny parallel inclusions, but by black carbon impurities that happen to form in the same pattern).
 

Massive chunks of transparent Beryl, usually Morganite and Heliodor, are sometimes carved into ornamental figures. Furthermore, perfect, transparent, six-sided crystals are occasionally worn uncut as rough necklace pendants.