Opal is one of the worlds most rare and unique gemstones. The combinations of colours and patterns within each stone makes opal a desirable gemstone for unique jewellery designs with no two stones being alike. As the colours are generated by light diffusion, opal is a stone that wants to be ‘moving’. It is well suited to being worn as jewellery as movement causes the colours to flash and change, catching the eye.
Opal is Australia’s national gemstone, with 80-90% of the world’s production of precious opal originating here. The extraction of precious opal is still largely an amateur mining pursuit, with the majority of miners being individuals or small partnerships working on small-scale claims.
A unique form of opal, often found in ironstone host rock found in the south and central west of Queensland. Usually very bright in colour and makes attractive jewellery, it can be any body-tone, from white though to black. Top examples are valuable.
Opal formed in a host rock. Often seen as flashes of colour embedded in a porous host. Commonly associated with Andamooka. Is often treated to make the host sandstone darker to bring out the colour play. Not considered gem-grade material.
Apart from Colour, Pattern and size, opal can be classified by the attributes of Body Tone and Brightness.
Body tone is graded as the background shade of the stone when viewed from the face. An N scale is used to identify body tone, with N1 being black and N9 being white according to the guide below.
Brightness is the strength of the colours in the face of the stone, with a B scale being used to classify the brightness according to the guide below