Larne Boyles/GIA Jane Coursin, a jewelry designer, gets an opinion of her opal ring from Damien Cody of Cody Opals.
Larne Boyles/GIA Damien (left) and Andrew Cody of Cody Opal of Australia, speak about opalized fossils during an event at GIA on June 10.

Take a receding ocean, some silica gel and a dying dinosaur and if left alone for about 100 million years or so, you’ll end up with one of Australia’s most prized possessions: an opalized fossil.

At least that’s one theory of how it happens, says Damien Cody, director of Cody Opal of Australia.

“There’s been more research done on opals in the last 12 months than ever before,” said Cody. “I’ll talk about three formation models (for opalized fossils), but at the rate this research is being done, that could all change tomorrow.”

The rare and natural phenomenon of opalized fossils was the focus of the lecture "Opal and the Dinosaurs: Discover the Link" by Damien and Andrew Cody of Cody Opal presented June 10 at GIA’s Carlsbad, Calif., campus. The lecture coincided with the opening of GIA’s latest museum exhibit of the same name.

It also marked the second installment in a four-part lecture series titled "Precious Paths: Surprising Links to Gemology." The event was hosted by GIA and the Gem & Jewelry Society of San Diego.

The Codys explained the history of Australian opal, from its prehistoric beginnings to when it was first discovered in 1863 with a slideshow presentation. Ninety-five percent of the world’s gem quality opals come from Australia due to ideal environmental conditions.

“The right geologic, biologic and climatic conditions need to coincide in order for opals form. So there are relatively few opal deposits in a few worldwide locations,” Damien said.

Currently there are five locations that mine opal: Australia, Brazil, Mexico and parts of the United States. The most recent opal mines have been discovered in Ethiopia. But Australia is the only locale where gem quality black opal is found.

The first opalized fossils were found in Australia in the late 19th century. Since then, many other fossils have been found, most being from ancient sea creatures left behind after the Eromanga Sea receded to reveal the Australian desert. 

In 1987, a nearly complete set of opalized fossils, a skeleton of a pliosaur, was found. It turned out to be the most complete set of opalized fossils in the world and the Australian Museum now displays it as one of its most prized exhibits, the Codys said.

In addition to fossils, the Codys discussed other unusual opal specimens they’ve discovered over the years. One such item is an opal specimen with a trapped water bubble. The bubble, which moves freely within the opal, is estimated to be 100 million year old.

In addition to the water bubble opal and the opalized fossils, the exhibit at GIA also includes fine specimens of black opal and jewelry. Opal and the Dinosaurs: Discover the Link will remain on display through January 2003.

GIA’s museum at the Carlsbad, California, campus is open to the public, 9 a.m.-4 p.m., Monday-Friday, except when the Institute is closed for holidays. For more information, call Laurie Stein, museum supervisor, at (760) 603-4033.