On 23 July 1993, the then Governor-General, His Excellency the Honourable Bill Hayden AC, proclaimed the opal as Australia’s national gemstone.
The finest opals in the world come from Australia. Precious opals can flash with all the colours of the rainbow, changing from red, orange, yellow, green, blue, indigo and violet when moved against the light.
In Dreaming Stories, a rainbow created the colours of the opal when it touched the earth. Also, known to Indigenous Australian peoples as the fire of the desert, the opal is a powerful symbol of Australia’s arid interior.
Australian opal forms when water containing dissolved silica seeps into openings in the rock. The water slowly dissipates and microscopic spheres of hydrous silicon dioxide form.
The importance of the opal
Australia’s opal fields are bigger than those found in the rest of the world combined, and support many communities in South Australia, New South Wales and Queensland.
Australian opals are valued for their stability as well as brilliance. Australia is the only place in the world where sedimentary opal has been discovered as well as opalised animal fossils. Most opals found outside Australia are associated with volcanic rocks and have a high water content.
Opal types
Australia’s precious opals include:
- Black opal, for which Australia is best known.
Its colours play from red, green, blue, violet, magenta or yellow against dark backgrounds like black, dark blue or dark grey. Most of the world’s supply of quality black opals come from the mines of Lightning Ridge in north-western New South Wales. - White opal, the most common type of precious opal, has vibrant colours that appear from a background that is white or milky. These gems are found at White Cliffs in New South Wales, and Coober Pedy and Andamooka in South Australia.
- Crystal opal is transparent or extremely translucent, with colours that appear from below the surface. White and crystal opal form the bulk of the precious opal supplied to the world from Australian fields.
- Boulder opal is a kind of white opal, found in veins and cavities in mudstone or sandstone. Queensland’s south-west opal fields, such as Quilpie, Yowah and Eromanga, have been important sources of boulder opal.