Gem Groups

Quartz

Quartz is a very commonly occurring gem. The best giant crystals are found in Brazil. From coarse sand to the finest amethysts there are many forms of quartz. Colourless rock crystal is the purest. Chalcedonies and jaspers are a form of fine-grained quartz. Iron, for example, gives the colour to amethyst and citrine. Citrine is actually amethyst which has been subjected to extreme temperatures, either naturally or in a laboratory. Smokey quartz is thought to have been exposed to radiation. Scotland is a well-known source of almost black smokey quartz, called morion, and extremely dark citrine called cairngorm. Chalcedonies are carnelian (cornelian), chrysoprase (marketed as Australian Jade) and agate.

Corundum

Rubies are true red corundum. Blue ones are sapphires, other colours are called sapphires as well. Sapphire is next to diamond in hardness. You may not realise that you have sapphires lying around the house if you have any of the old-fashioned emery boards. Emery is impure corundum.

Beryl

Beryl is known as aquamarine and emerald. But one is considerably more valuable than the other! Pure beryl is actually colourless. Emerald has been prized for millennia. Cleopatra was known to have several lucrative emerald mines.

Opal

Opals are known as unlucky stones but in Roman times they were seen as symbols of power. The Aztecs mined Fire Opal. During the 14th century in Venice, people noticed that opals became more brilliant when wearers caught the Plague and dulled when a person died. This helped reinforce the belief that opal was unlucky.

Organic Gems

Organic gems include jet, amber, coral and pearl. Jet is formed from ancient wood and amber is formed from the sap. Jet was hugely popular in Victorian times as mourning jewellery, but it is no longer as valued.

Minerals

Minerals can even be found in the form of crystals although they are not common. Silver used to be more valuable than gold in medieval times, and even today gold is not the most valuable metal in jewellery — it is platinum. In alchemy, platinum was believed to be a mixture of gold and silver.