While the headlines of the gemstone world often focus on the ‘cornflower blues’ of Kashmir or the ‘royal blues’ of Sri Lanka, the research published in The Australian Gemmologist reveals a more complex and scientifically fascinating story.
From the basaltic ridges of New South Wales to the vast gemfields of Central Queensland, Australian sapphires represent a unique intersection of volcanic history and gemmological rarity.
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Rough gemstone concentrate from Kings Plains. Photo provided
by the GAA courtesy of John Wilson. |
Australian sapphires are primarily ‘basalt-related’. Unlike metamorphic sapphires found in marble or gneiss, Australian gemstones are ‘xenocrysts’. This means they did not form within the basalt itself; rather, they were created deep in the Earth’s upper mantle and were later ‘hitchhikers’ carried to the surface by rising alkaline basaltic magmas during the Cenozoic era, which is after the time of the dinosaurs.
This magmatic origin is responsible for the distinct chemical fingerprint of Australian sapphires. These gemstones typically have higher iron content than their metamorphic counterparts. This iron presence results in the ‘BGY suite’ —a spectrum of blue, green, and yellow—that defines the Australian output.
While it traditionally produced darker blues, this same chemistry allows for the creation of the highly prized ‘parti-colored’ sapphire, where two or three distinct colours appear in a single crystal.
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| Above: Map showing the distribution of sapphire fields in eastern Australia. Adapted from Sutherland et al. (2016). |
The most significant production areas are the gemfields in Central Queensland, including Anakie, Sapphire, Rubyvale and The Willows, Lava Plains in Northern Queensland and the New England region of New South Wales.
The Anakie field, exploited for more than 100 years, is celebrated in the journal for producing some of the world's finest golden yellow and large ‘black star’ sapphires. Conversely, the New England region — specifically the areas around Inverell and Glen Innes — was once the source of nearly 70 per cent
of the world's sapphire supply.
In The Australian Gemmologist, contributors such as Robert Coenraads and Terry Coldham have documented the Kings Plains deposit, arguably the richest single accumulation of gem-quality sapphire ever discovered.
Unfortunately, all these NSW mines have closed due to rising mining costs and lower recovery rates.
Specific internal features characterise Australian sapphires.
Strong colour zoning: Many gemstones exhibit sharp, angular bands of colour, a result of the changing chemical environment during the crystal’s growth.
Silk and inclusions: The presence of ‘silk’ - fine rutile needles - and ‘dust-like’ clouds is a common feature. Mineral inclusions such as zircon, feldspar, and columbite-tantalite are often cited as diagnostic markers of their magmatic origin.
Dichroism: Australian gemstones often show a marked shift from blue to greenish-blue when viewed through a dichroscope, a trait that requires expert cutting to ensure the most attractive colour is centred.
Historically, Australian sapphires were often dismissed as too dark. However, recent shifts in consumer taste have vindicated the local treasure. The rise of ’parti-sapphires’ and ‘teal’ gemstones, which were once discarded as off-colour, are now some of the most sought-after varieties in modern jewellery design, thanks to social media and changes in fashion.
While commercial mining has declined from its 20th-century peak, the Australian fields still hold significant untapped resources. As the industry moves toward ethical sourcing and traceability, the Australian sapphire remains a benchmark of durability, beauty, and scientific intrigue.
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