The beryl group of minerals and gemstones
Minerals in the beryl group are silicates
of beryllium and aluminium, having the chemical formula Be3Al2(SiO3)6. Beryl is found as barrel-formed crystals. The hardness of the crystals are of the grade
7.5 - 8.0. on Mohs scale. Beryl is usually found in granitic pegamitic
rocks. The crystals of beryl are six-sided (hexagonal) columns.
Beryl often contains dissolved elements giving
colour to the crystal. Beryl without distinct inclusions and without
uneven colour are used as gemstones. Beryl not of gemstone quality
is most often called only beryl. There are the
following types of beryl gemstones differing in their colour:
Emerald: This is deep green beryl. Larger specimens without easily visible inclutions of
foreign materials are rare and expensive. The colour is produced by cromic oxide
dissolved in the crystal substance. Vanadium and iron may also effect the
colouring shade.
Aquamarine: Aquamarine means sea water. The colour is skyblue, sea blue or greenish blue.
The colour is due to traces of iron in the crystal framework.
Morganite: This variant has a pink color. It is an extreemely rare and expensive stone.
Bixbite: This is red beryl. Like morganites, specimens are rare and expensive.
Golden beryl: This variant is golden yellow.
Goshenite:
This is coluorless beryl. It is found at the place Goshen in massechusets. Even
though the variant is rare, the value is moderate due to lack of optical refractive brilliance.