More than 80% of Australia’s total production of gem quality opal is light opal which is mined in the Coober Pedy,Mintabie and Andamooka areas of South Australia. Only 20% of available opals are of the boulder and black opal varieties.

Boulder opal is unique to Queensland and is found in the mining belt stretching from Quilpie in the south-west to Winton in the north of the State.

Black opal originates from the rich mining fields of Lightning Ridge in northern New South Wales.

Opal is one of the rarest of precious gems, with its' annual production far less than diamonds, sapphires and emeralds. Added to this, the Australian opal has a most unique appearance, characterised by a display of sparkling prismatic colours as the stone is moved through different light.

Our Prehistoric Gem
Opal was originally formed during the tertiary period of history, some 15-30 million years ago. Before it became the beautiful gemstone we know today, opal started as a liquid gel which seeped through the top sedimentary layers of the earth until it reached the impervious clay level some 30 metres down. Here over millions of years, this liquid gel hardened to form deposits of precious opal.

Scientific Composition of Opal
Scientifically, opal is composed of minute particles of silica, closely packed in transparent spherical arrangements. Light passing through these spheres is scattered, causing the diffraction of white light into its various base colours of red, orange, yellow, green, blue, indigo and violet. This is similar to the effect of a rainbow or white light passing through a prism.

In chemical terms, opal is made up of hydrated silica with a varying water content between 6-10%. The chemical composition is Si O2 n H2O. Opal is the only gemstone with an amorphys non-crystalline structure, typified by a random irregular pattern. This is one reason why no two opals ever look the same.