Rare $675,000 opal makes public debut

A rare, $675,000 opal has gone on display at the South Australian Museum, the first time it's being shown in public since its discovery in 1946.

South Australian Museum

The 998-gram gem, called the <a href="https://www.samuseum.sa.gov.au/media/53865/worlds-finest-piece-of-uncut-opal-finds-new-home-at-the-south-australian-museum" target="_blank" target="_blank">Fire of Australia</a>, is the largest known piece of high grade opal in the world, according to the museum. "The Fire of Australia is around the size of a softball... and shows all the colors of the spectrum," museum director Brian Oldman told CNN.

The 998-gram gem, called the Fire of Australia, is the largest known piece of high grade opal in the world, according to the museum. "The Fire of Australia is around the size of a softball... and shows all the colors of the spectrum," museum director Brian Oldman told CNN.

First discovered in 1946 by miner Walter Bartram at the Eight Mile opal field in <a href="https://www.cooberpedy.sa.gov.au/tourism#.WImbt7Z95PU" target="_blank" target="_blank">Coober Pedy</a> -- a small desert town in northern South Australia famous for its opals. The opal remained in the Bartram family for more than 60 years.

First discovered in 1946 by miner Walter Bartram at the Eight Mile opal field in Coober Pedy -- a small desert town in northern South Australia famous for its opals. The opal remained in the Bartram family for more than 60 years.

Opals are highly colored, semi-precious stones that form from closely packed silica deposits found in the dry ground of arid regions.

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Prized for its flashing, rainbow-like hues, the <a href="https://www.gia.edu/" target="_blank" target="_blank">Gemological Institute of America (GIA)</a> classifies the gem according to <a href="https://www.gia.edu/opal-description" target="_blank" target="_blank">five main categories</a>: fire opal, white opal, black opal, boulder opal and crystal opal.

Prized for its flashing, rainbow-like hues, the Gemological Institute of America (GIA) classifies the gem according to five main categories: fire opal, white opal, black opal, boulder opal and crystal opal.

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The outback mining town of Coober Pedy in South Australia supplies around 90% of the world's opal supply.

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Here, an opal expert in Coober Pedy displays a harlequin crystal opal (left) and a boulder opal.

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The South Australian Museum has one of the world's largest opal collections, including this stone, called the Candle of Life. An opalized ancient cuttlefish fossil, this opal is similar to the Virgin Rainbow, but is not pure crystal opal.

South Australian Museum

"South Australia has the perfect climate for opal creation and many of our pieces are the result of opal forming and replacing the fossils of ancient sea creatures" Oldman said. "So, where you see a specimen that seems to echo shapes of an ancient creature and pieces that look like a sea bed, like this Crouch opal, that is because our land made it possible for opal to form and fill in spaces left behind behind animals, water, shells, et cetera."

South Australian Museum

The largest and most valuable single piece of rough gem opal is the <a href="http://www.opalsdownunder.com.au/learn-about-opals/introductory/famous-opals" target="_blank" target="_blank">Olympic Australis</a> (not pictured), a 3.4 kilogram, 17,000 carat stone estimated to be worth about $1.9 million.

The largest and most valuable single piece of rough gem opal is the Olympic Australis (not pictured), a 3.4 kilogram, 17,000 carat stone estimated to be worth about $1.9 million.

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In terms of polished stone, the <a href="http://www.samuseum.sa.gov.au/explore/exhibitions/opals/opals-media-releases" target="_blank" target="_blank">Virgin Rainbow</a> is the world's most expensive opal on a per gram basis. Valued at over $750,000, the opalized fossil (pictured) is the shape and size of an index finger, and was named for the multitude of colors that can be seen in the stone.

In terms of polished stone, the Virgin Rainbow is the world's most expensive opal on a per gram basis. Valued at over $750,000, the opalized fossil (pictured) is the shape and size of an index finger, and was named for the multitude of colors that can be seen in the stone.

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CNN —

The world’s finest uncut opal, a 998-gram gem called the Fire of Australia, has gone on permanent public display for the first time since its discovery more than 60 years ago.

Valued at more than $675,000, the stone is the largest known high-grade opal in the world, according to the gem’s new owners, the South Australian Museum in Adelaide, Australia.

“The Fire of Australia is around the size of a softball…and shows all the colors of the spectrum,” museum director Brian Oldman told CNN, emphasizing the extreme rarity of the stone.

“The opal is unique because of its high quality and large size. It throws off a lot of red, which is one of the indications of a highly valuable piece of opal.”