Opals are Australia's national gemstone

Australia currently produces about 95 per cent of the world’s precious opal from widely scattered fields throughout central Australia. No other country on Earth has such an abundance of this rare precious gemstone.

The sedimentary opal deposits of central Australia occur along generally flat-lying horizontallayers within 30 metres of the earth’s surface. They are a product of a unique set of geological events which occurred over a 100 million year period.

Australia ’s precious opals include the black opal (produced in Lightning Ridge, New South Wales), white opal (majority of the world’s production occurs in Coober Pedy, South Australia), crystal opal and boulder opal (mined in Central Queensland).

In Aboriginal legend, the mesmerising opal was a gift from the sky, from a rainbow that had touched the earth and created the colours of the opal.

Source: What Is Opal and Prime Minister of Australia - Australia in Focus - Symbols and Icons - National Symbols