What is opal?

Opal is a mineral that belongs to a large group of minerals known as the “Silica family”. Silica, known by its chemical formula as “SiO2”, is a mineral compound of two atoms; Silicon and Oxygen. The most common forms of Silica in our environment are crystals of Quartz, or sand, and also window glass.

Opal is unique however as it also has in its formula a component of water or ‘H2O’ making it’s complete formula, SiO2,nH2O. When we look at the letter ‘n’ in the formula it relates to “how much” water is there. For more of the chemistry you should have a look at the “Sciences” tab.

Another special feature of opal is we describe its structure as “amorphous” or without form. This is from a mineralogical and atomic point of view. Quartz for example has a crystalline structure which goes deep down into its arrangement of atoms. Opal on the other hand does not have this regular structure at an atomic level. However it does have a magnificent structure all of its own. and for that you will have to visit the “sciences” and “gemmology” tabs to find out more”. Also a visit to the ‘history” tab will give you an insight into the role of Australian Scientists into this amazing gemstone.

What makes opal a special gemstone?

Precious opal as a gemstone is known worldwide as Australia’s National Gemstone and this is because Australian opal fields produce commercially the highest quality, and most valuable precious opal gemstones compared with any other source in the world. Without a doubt, the most striking thing about a precious opal is it’s distinctive ‘play of colour’. It’s ability to diffract light results in rainbow like colours from every angle.

Why the name Opal?

Numerous texts state that the derivation of the word “opal” comes from the Sanskrit word “upala” although this appears to be the general name given for “precious stones” (Skertchley). In Greek language, in the first century before Christ, the gemstone was known as “opallios”. In Indonesia opal was known as “Kalimaya” a name also derived from the Javanese word “Kali” meaning a “river” and the Sanskrit “maya” meaning “an illusion” and hence the stone was a “river of illusion”. The Aztec name given to early Mexican opals was “vitzitziltecpatl” meaning “Hummingbird stone” as the colour change of precious opal was likened to the changes of colour seen in the birds’ plumage.

Where is opal found?

Common varieties of opal are found all over the world and in many different localities and environments, perhaps this is why it is called common opal. Precious opal is found in fewer locations worldwide. However the most important source of precious opal is in Australia. Perhaps the second most important source of precious opal is now the country of Ethiopia in north eastern Africa. In recent times Ethiopia has become a substantial source by volume of precious opal.