The National Significance and Global Appeal of Australian Precious Opal

More than a striking gemstone, Australian opal holds a unique place in the nation’s identity.

As Australia’s national gemstone, opal is an enduring emblem of natural beauty, ancient history, and cultural identity. Officially recognised in the Australian Symbols booklet, published by the Department of Prime Minister and Cabinet, opal stands alongside the national flag, coat of arms, colours and floral emblem – as a nationally significant and internationally recognisable Australian symbol.

While opal is found in several countries, Australian precious opal stands apart for its singular beauty, rarity and connections to deep time and culture. It comes from a continent inhabited continuously by First Nations peoples for tens of thousands of years, and from landscapes witness to hundreds of millions of years of geological and ecological evolution.

Since the late 1800s and early 1900s, when mining began in earnest in the remote outback, Australian opal has dominated the global market. The vibrant, resourceful culture of opal prospecting and mining continues to shape the national character.

A national symbol must have broad relevance. In Australia, there is commercial opal production in New South Wales, Queensland and South Australia, and minor occurrences in Western Australia. Globally recognised localities include Lightning Ridge, White Cliffs, Quilpie, Yowah, Coober Pedy and Andamooka. These remote and storied places, all associated with the Great Artesian Basin, are known for their isolation, harsh climate and stark beauty – hallmarks of  Australia’s vast interior and national identity.

Although opal mining is relatively recent, the geological conditions producing Australian precious opal are ancient, dating back more than 110 million years to when much of central Australia was covered by an inland sea and formed part of the supercontinent Gondwana. Opal, often described as a stone of rainbow colours, features in First Nations stories, including those of the Rainbow Serpent. Rare opalised fossils further deepen its scientific and cultural significance, offering tangible connections with Australia’s deep past.

Gemmologists classify opal into two main types: common opal and precious opal. Precious opal – which displays the dazzling phenomenon known as play of colour – is the more celebrated and valuable. Unlike crystalline minerals, precious opal is amorphous, with its spectral colours caused by light diffracting through an orderly array of silica spheres. In Australia, commercial opal deposits occur in sedimentary rocks.

Common opal, by contrast, lacks play of colour, though it may show attractive hues, patterns and optical effects in its body colour. Sometimes described as ‘ornamental’ rather than ‘common’, it is found in various global locations. Examples include Peru’s pink opal and Indonesia’s green-blue varieties. Common opal typically forms in volcanic environments and may exhibit some micro-crystallinity.

Valuing precious opal is complex. A key factor is body tone – classified as black, dark or light – with black opal being the most highly valued for its striking contrasts and vivid colours. Other value factors include the brightness, directionality and consistency of the play of colour, the spectral colours present, and the distinctiveness of their patterns.

One of precious opal’s most exciting properties is that no two stones are alike. This celebrated variety and diversity can present challenges to those striving for expertise in assessing opal, including separation of natural opal from synthetics and simulants.

To support greater expertise in this area, the Gemmological Association of Australia (GAA) has developed the GAA Certificate in Opal Studies. Delivered in partnership with the Austrlian Opal Centre, this self-paced online course provides comprehensive, up-to-date knowledge for anyone buying, selling, valuing, collecting, or simply fascinated by opal.

Australian precious opal symbolises the colourful spirit and story of Australia, including – to quote the national anthem – its “beauty rich and rare”. To wear it is to wear not just a symbol of Australia, but a piece of this ancient and beautiful land.

NATALIE HAMBLY is a Sydney-based writer and gemmologist with a background in journalism and media. The GAA OPAL COMMITTEE is a specialist group at the Gemmological Association of Australia.