Australian Opal

Opal Introduction and Formation

Precious Opal is a gemstone. The word opal comes from the Greek word “Opallos” meaning to change colour. It is the only gemstone known that has the unique natural ability to diffract light.

Opal is estimated to have begun formation during the Cretaceous period (65-140 millions years ago). Central Australia was an inland sea in millions of years ago. As weather conditions changed and the sea gradually disappeared, the sand sediments released large quantities of soluble silica, creating a gel. This gel seeped into cracks and crevasse in the ground and gradually hardened to form opal.

Opal is composed of silica spheres that are packed together. In precious opal, the arrangement of spheres is an orderly three-dimensional grid. Light passing through the transparent spheres is scattered by the array of voids. White light is diffracted and split into its various colours at different angles.

Different Types of Opal

Black opal is the rarest and most valuable type of natural opal found in the world. Black opal is only mined in Australia, mainly from the Lightning Ridge area of northern NSW. Black opal gets its name from its dark body. However, it contains brilliant flashes of red, blue, green and orange.

Boulder opal is similar to black opal with its appearance and display of brilliant colours. The only difference between the two is that boulder opal occurs within the ironstone and sandstone boulders common to Quilpie and Winton in central Queensland where it is found. This boulder is often included as a base in boulder opal jewellery settings together with the opal gemstone face.

This solid opal gemstone primarily emerges from the famous mining area of Coober Pedy in South Australia. Similar to black and boulder opal, light opal features brilliant internal colours but rather than a dark body this gemstone has a milky or “light” appearance.

Light opal sometimes forms in a fragile thin layer but with brilliant colours. This type of natural opal can be strengthened with a supporting base of a dark material such as ironstone to create a gemstone suitable for fine jewellery. The resulting doublet opal is often quit large, shows spectacular colour but is less expensive than weightier solid varieties.

An extension of doublet opals is the triplet opal. This type of opal features a layer of natural opal covered by a transparent crystal dome. This technique of supporting and protecting the precious stone from above and below, permits the use of thin, delicate pieces of natural opal. Accordingly, these often brilliantly-coloured triplet opals feature in entry-level opal jewellery and make excellent gifts.

Opal Care

Precious opals usually contain 6-10%water. The water content of opal is easily lost if the stone is heated, causing it to crack or craze and to lost colour and/or clarity. Opal can absorb fluids, and should not be brought in contact with detergent or oils.

Doublets or Triplets are not recommended to be immersed in water. There is a special bonding cement hold the opal slice in place. Although this cement is designed to make the Doublets or Triplets waterproof, care should be taken. Please remove your opal jewellery before entering a shower, especially in hot water.

Violent impact with hard surfaces will cause defects on your opal jewellery. It is recommended to store opal jewellery separately from other jewellery. Always use a soft cloth to clean and polish your opal jewellery and do not expose it to high temperature environment.