Australia became a major diamond producer in the 1980s, almost entirely because of one mine: Argyle in the Kimberley region of Western Australia. Argyle produced enormous volumes of small brown diamonds and a tiny stream of pink stones that became famous worldwide. It closed in 2020. Smaller operations at Ellendale and Merlin added yellow diamonds and a few large stones to the country's record.
Early finds
Diamonds turned up in Australia long before any big mine existed. Gold miners in New South Wales found small stones in alluvial gravels in the 19th century, and the Copeton and Bingara area produced modest amounts of alluvial diamonds in the late 19th century. These deposits were small and the stones were hard to sell, so Australia stayed a footnote in the diamond world for about a century.
The picture changed in the 1970s, when prospecting companies began a systematic search of the Kimberley in the far north of Western Australia. Geologists sampled stream sediments for diamonds and for indicator minerals that hint at a diamond-bearing pipe upstream. Those methods are covered on the diamond geology page.
Argyle
Prospecting teams found diamonds in Smoke Creek in 1979 and traced them upstream to their source, a pipe near Lake Argyle in the eastern Kimberley. The deposit, known as AK1, came into production in 1983 from alluvial gravels, and open-pit mining of the pipe itself followed in 1985. The operating company eventually came under the full ownership of Rio Tinto.
A lamproite pipe
Argyle broke the rule that big diamond mines sit in kimberlite. Its host rock is olivine lamproite, a different kind of volcanic rock that also comes from deep in the mantle. The pipe also lies at the edge of an old block of continental crust, outside the stable craton interiors where most rich kimberlites occur. Argyle forced geologists to widen their search models, and lamproites became prospecting targets in their own right.
Volume over value
For much of the late 1980s and 1990s Argyle produced more diamonds by carat weight than any other mine in the world. Most of that output was small and brown, and much of it was industrial or low-grade gem quality. The average value per carat was low. Argyle's operators helped create a market for brown diamonds by grading and marketing them under color names such as "champagne" and "cognac." Many of the small stones were cut in India, which grew the cutting industry around Surat; see Gujarat and Surat diamond cutting.
Argyle pink diamonds
Pink diamonds made up a minute fraction of Argyle's production, often described as less than one percent of output by weight. They gave the mine its reputation. Argyle became the main source of pink diamonds in the world, along with small numbers of red, violet and blue stones. The pink color is linked to plastic deformation of the crystal lattice during the diamonds' long history in the mantle, a cause of color explained on the page on fancy colored diamonds.
From 1984 the best pinks were offered each year at the Argyle Pink Diamonds Tender, an invitation-only sale of a few dozen polished stones. Tender diamonds were cut, graded and laser-inscribed, and they reached very high prices per carat.
Underground mining and closure
The open pit reached its practical limit in the 2000s. Rio Tinto then developed an underground block cave beneath the pit, a method described in how diamonds are mined, and production moved underground in the early 2010s. The orebody was finite, and Argyle stopped mining in November 2020 after 37 years of operation. Rehabilitation and closure work on the site followed. The end of Argyle removed the world's main source of pink diamonds, and stones with documented Argyle origin have since drawn strong collector interest.
Ellendale
Ellendale, in the West Kimberley east of the town of Derby, is a field of lamproite pipes discovered in the 1970s. Commercial mining ran from the early 2000s until about 2015, with a change of operator along the way. Ellendale became known for fancy yellow diamonds, and for several years an agreement with Tiffany & Co. covered much of the yellow output. The deposit's other production was mostly white and off-white stones. Yellow color in diamonds comes from nitrogen in the crystal, which the page on diamond chemistry and formation explains.
Merlin
Merlin lies in the Northern Territory, south of the Gulf of Carpentaria. It is a cluster of small kimberlite pipes found in the early 1990s. Mining began in the late 1990s and ran only for a few years, and later owners have tried to restart it more than once. Merlin's best-known result is a diamond of about 104.73 carats recovered in 2002, the largest diamond found in Australia.
Australia in the world diamond trade
At its height Argyle put Australia near the top of world production by carat weight, though well behind countries such as Botswana and Russia by value. After Ellendale and Argyle closed, Australian output fell to a small fraction of its former level. The country's legacy lies in Argyle's pinks and in the geological lesson that lamproite can host a world-class mine. For a comparison with other producing countries, see diamond mines of the world, and for the high-latitude mines that rose during Argyle's later years, see diamond mines of Canada.
Frequently asked questions
When did the Argyle diamond mine close?
Argyle ceased mining in November 2020 after its orebody was exhausted. It had operated since 1983.
Why are Argyle pink diamonds so rare?
Pink stones were a tiny fraction of Argyle's production, and the mine was the world's main source of them. With Argyle closed, no other mine has replaced that supply.
What rock were Argyle's diamonds found in?
They came from olivine lamproite, a mantle-derived volcanic rock. Argyle was the first major diamond mine hosted in lamproite instead of kimberlite.
Does Australia still produce diamonds?
Production fell sharply after Argyle and Ellendale closed. Small projects and restart attempts have come and gone, but Australia has not returned to its former scale.