Over 90% of the world's precious opal comes from Australia and opal is Australia's national gemstone
Precious opal is defined as opaline silica with a play of colour. The term play of colour was created solely to describe opal's beautiful shifting of spectral hues. Australian opal is referred to as "sedimentary opal" because it is hosted predominantly by sedimentary cretaceous rocks overlaying the Mesozoic Great Artesian Basin. Australian precious opals usually contain around 5-6% water and consists of small silica spheres arranged in a regular pattern. Its hardness of 5.5 to 6.5 on Moh's scale puts it about half way down the range (roughly the same hardness as glass). It has a specific gravity of 1.9 to 2.3 depending on the amount of water present.
Black opal is found mostly around Lightning Ridge, New South Wales.
Boulder Opals are found through out the vast expance of the Queensland outback in isolated deposits.
Matrix opal is found on most boulder opal fields fith the best comming from Koriot and yowah opal fields.
Pipe opal is generally found in association with boulder opal deposits.
Opalized replacements of wood or found and are rarely of gem quality.
Opals for sale on this site are natural solid Australian opals. With the exceptions of the "sandstone matrix opal" ("fairy opal"), this a natural occuring material that has been carbonized and stabilized to enhance the colours (see "Types of Australian opal")And Sandstone pipe opals have had the sandstone stabilized by the injection of a polymer pesin into the sandstone to maintain the entegrity of the gem durring setting and is mentioned in the text.
We do not "fracture fill" our opals. If an opal has a flaw it will be mentioned in the text.
95% of Opals on this site are mined by ourselves the other portion is from Koriot or yowah as we love this type of matrix ourselves.
