'Finest Opal Ever' to Make Its World Debut at the South Australian Museum in Adelaide

Billed as the "finest opal ever," the Virgin Rainbow will make its world debut at the South Australian Museum in Adelaide in September as the centerpiece of a larger exhibition to commemorate the centenary of opal mining in the Land Down Under.

Measuring 2.4 inches long and displaying a full spectrum of brilliant color, the finger-shaped specimen seems to have a light source all its own.

"It's almost as if there's a fire in there," museum director Brian Oldman told AFP. "You see all different colors. As the light changes, the opal itself changes. It's quite an amazing trick of nature."

Veteran miner John Dunstan is credited with discovering the Virgin Rainbow in the desert soil of Coober Pedy in South Australia in 2003. Dustan has mined opals for 50 years, but the internal fire of the Virgin Rainbow is unlike anything he's ever seen.

"That opal actually glows in the dark," he told ABC North and West SA. "The darker the light, the more color comes out of it. It's unbelievable."

Dustan explained that the Virgin Rainbow is a Belemnite pipe, which is essentially an opal that formed in the skeleton of an extinct ancestor of the common cuttlefish. He found it while digging into the tailings of an old mineshaft. At first, it didn't look like much because it was covered in sandstone. But, as Dustan cleaned it off, he realized he made a once-in-a-lifetime discovery.

"I knew it was one of the best ever," he said. "You'll never see another piece like that one, it's so special.

Dustan had intended to sell his magnificent opal at auction and was confident it was worth at least $1 million Australian dollars ($730,000). But when the bids did not meet his minimum, he decided to sell the gem to the South Australian Museum 18 months ago for an undisclosed amount. The deal would ensure that the opal stayed in Australia.

Coober Pedy is often called "The Opal Capital of the World." In 1915, a 14-year-old boy named Willie Hutchison was on a gold mining expedition with his father when he happened upon precious opals. Legend states that young Willie was instructed by his dad to stay at the camp but, instead, the young man set out to search for water. He eventually returned to camp with water and precious opal gemstones.

That discovery sparked a rush of mining activity that has generated top-quality gems for the past 100 years. Australia, in fact, produces more than 90% of the world's precious opals.

Scientists claim that between 100 million and 97 million years ago, Australia's vast inland sea, which was populated by marine dinosaurs, began retreating. As the sea regressed, a rare episode of acidic weather was taking place, exposing pyrite minerals and releasing sulphuric acid. As the surface of the basin dried further and cracked, silica-rich gel became trapped in the veins of the rock. Over time, the silica solidified to form opals.

Oldman believes that the new "Opals" exhibition at the South Australian Museum will be a memorable event — the finest collection of precious opals to have been brought to one place in the world. The exhibit runs from September 25, 2015 through February 14, 2016.

Photo by Richard Lyons, courtesy South Australian Museum.