The main varieties of Australian Opal available in jewellery shops or specialist Opal outlets are listed below.
Precious Opal that has a black appearance when viewed from the front. Only Opal that has a body tone of N1-N4 can be called Black Opal. Rarer than light or dark Opal.
Usually Lightning Ridge area in NSW or more rarely Mintabie in South Australia.
White or light in appearance. Most abundant and affordable.
Usually South Australian Opal fields and also found in some from other areas.
Andamooka Matrix Opal
Black or darkish bodied Opal with bright specs of colour. This is chemically treated Limestone matrix with precious Opal in voids. Not common.
Andamooka Opal field in South Australia.
Translucent appearance - a printed page would be roughly visible through the stone. Relatively abundant.
Most Opal fields
Usually a thin layer of precious Opal naturally adhering to brown ironstone host rock. Relatively abundant.
Queensland Opal fields
Precious Opal with a grey or darkish appearance when viewed from the front. Dark Opal is relatively abundant.
Usually Lightning Ridge area in NSW or Mintabie in South Australia.
In addition to solid Opal, a number of other varieties composite Opal are widely available. Composite stones are generally more affordable than solid stones as smaller amounts of precious Opal are used. In all cases, thin slices of Opal are glued to a backing of black backing material.
While most composite stones are made from natural Opal, occasionally synthetic Opal is used in doublets or triplets. Consumers should ask the supplier to confirm whether Opal used in composite stones is natural. Also note that whilst composite stones generally have the appearance of black Opal, none can be correctly described as Black Opal.
Thin slice of precious Crystal Opal glued to black backing material. When the backing is brown ironstone it is often called a Boulder Doublet.
Thin slice of precious Crystal Opal glued between a crystal cap on top and a black backing.
Thin chips of precious crystal Opal glued onto a black backing. It can be used in Opal Doublets, Triplets or on watch faces.
Small thin pieces of precious crystal Opal glued directly into channels in jewellery.