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A Guide to Our Gemstones - Part One

Introduction to Gemstones


Aquamarine
This gemstone is the blue or blue-green variety of beryl. Beryl is found in other colours including green (emerald) and pink (morganite). The name aquamarine means "water of the sea" and in ancient times, it was believed to protect sailors from shipwreck. Gem quality aquamarine is found in Russia, Brazil and USA. It has a hardness of 7.5 - 8.

Amazonite
This mineral is a blue green variety of microcline, named amazonite after the river Amazon. The gem quality material is found in USA, Russia and Brazil. Amazonite has a hardness of between 6 and 6.5.

Amber
Can be described as a mineraloid or an organic gem. Amber is the fossilized resin of ancient coniferous trees, dating from over 40 million years ago. The resin that oozed from these trees sometimes trapped insects, leaves, flowers and even small animals, their hardened and preserved remains can be seen today.

The largest source is from deposits found along the Baltic coast, it can also be found in the Dominican Republic. Amber can acquire an electric charge when rubbed, which has traditionally been used to identify it. It has a resinous lustre with a hardness of between 2 and 2.5.

Amethyst
A purple variety of quartz, the colour being due to the presence of iron. Often occuring in alluvial deposits or large geodes. It's natural colour varies from deep violet to mauve, heat treatment causes the colour to change to a golden brown and stones treated in this manner are often sold as citrines. Some natural amethyst stones exhibit both purple and brown colouration and can be known as ametrines.

It was used by the ancient Egyptians and it's name is said to derive from ancient Greek meaning 'not drunk" as the stone was said to prevent drunkeness.

Gem quality amethyst is mainly found in Brazil, Russia and South America. Amethyst has a vitreous lustre with a hardness of 7.

Aragonite
An unstable form of calcite, aragonite can be found in caves as stalactites, around hot springs or in mineral veins. Mollusc shells are partly composed of aragonite or calcite in conjunction with an organic substance called conchiolin.

Gem quality crystals have been found in Czechoslovakia. It is a relatively soft mineral with a hardness of only 3.5 - 4.

Aventurine
A type of quartz which can have a sparkly appearance due to inclusions within it, it is commonly green or brown. It is found in Russia, India, Brazil and USA. Aventurine has a vitreous lustre and a hardness of between 6.5 and 7

Azurite
A secondary mineral which is formed by the oxidization of other copper minerals. It is often found in conjunction with malachite and the presence of these minerals is a good indication of the presence of copper ores nearby. Azurite can form fine crystals.

It was ground and used as a blue pigment in Renaissance times, but was not as costly as ultramarine. Heating destroys azurite, turning it into black copper oxide. It is quite a soft mineral, having a hardness of between 3.5 and 4

Black Onyx
A variety of agate (chalcedony) which has black and white banding. It can also be produced by dying paler agates. Onyx has often been used for carvings and cameos, as a skilled carver can reveal the contrasting colours in the stone. Natural onyx is found in South America and India. It has a hardness of 7.

Blue Lace Agate
A variety of chalcedony. Many agates form in cavities within ancient lava flows, the colour being determined by the impurities that are present. Blue Lace Agate has shades of pale blue and white in concentric bands and is found in South Africa

Butter Jade
Also known as butterstone, this stone is no relation to true jade. It is found in the north of Africa and is sometimes used for carvings. Butter Jade has a hardness of between 6 and 8.