Opal is a hydrated silica mineral, it’s composed of submicrospic silica spheres that are bonded together with water and additional silica.
Sometimes the water in Opal can evaporate, creating cracks in the stone. Some, but not all Opals exhibits the play of colour known as ‘fire’. This is caused by the Opal’s minute silica spheres being packed in a formation regular enough to cause light diffraction.
The Opal is derived from the Latin opalus and the Sanskrit upala, meaning ‘precious stone’. Precious Opals were mined in the former Czechoslovakia at least as long ago as the fourteenth century. Mexican Fire Opal was used by the Aztecs and was brought to Europe by the conquistadors. In Roman civilisation, Opal was linked with good luck and hope.

Today the fast majority of Opal comes from Australia.