Disclosure of opal mine may trigger rush to Wyoming.

Reprinted from an article in the Denver Post, March 01, 2005

     by Katy Human
     Denver Post Staff Writer

The discovery of a 34-pound opal in central Wyoming could trigger an old-fashioned mineral rush this week.

On Friday, the Wyoming State Geological Survey will publicly release the location of an enormous opal deposit found near Riverton in central Wyoming, probably one of the biggest opal formations in the country, said Dan Hausel, a state geologist.

The giant opal is a common type, not particularly valuable itself, experts said. But its discovery raises the possibility that the deposit hosts substantial amounts of fiery orange opal and the precious iridescent variety. Geologists already have seen traces of these more valuable types.

Gem mining is notoriously unpredictable: Valuable veins of precious opal may - or may not - twist unseen through the more common variety of opal found at the new site.

So it's possible no one will express much interest, Hausel said.

But the claimants may line up Friday, high-tailing it from the state geology office to the opal site, throwing down corner stakes and racing to file paperwork with Fremont County.

"The thing that amazes me is that people haven't already staked claims out there," Hausel said. "There's hundreds of thousands or millions of tons of opal in there - fire opal, traces of precious opal. ..."

Opal is thought to form over hundreds to millions of years, after water percolates through silica-rich rock, drawing out minerals. In certain circumstances, the minerals drop back out of the water, forming opal's watery mixture of silica dioxide streaked with minerals.

"Volcanic rocks, that's where the best opal comes from," said Jim Cappa, a geologist with the state of Colorado.

In Colorado, rockhounds have plucked fairly nice opal from Specimen Mountain in Larimer County and elsewhere, he said.

"It's widespread. But when you think of gem-quality opals, those come from Mexico and Australia," Cappa said.

One Wyoming rockhound was skeptical that the new area - about 14 square miles of sagebrush scrub hills - will turn into a productive one for opal miners.

There are three grades of opal, said Melvin Gustin, who lives outside of Riverton and runs a small rock shop and jewelry business with his wife.

Common opal is a fairly unimpressive milky-white rock, he said; fire opal glows orange or red; and precious opal, the most valuable, glimmers with iridescence.

"I've never seen any fire opal here," Gustin said. "Now, that's what the world's seeking. I don't think it's worth claiming myself."

But Hausel has found the fiery variety, and he e-mailed a reporter images of rock with tantalizing streaks of iridescence.

"Well, I won't pooh-pooh this," Gustin said.

In the gem and mineral game, he said, there are always optimists willing to spend the few hundred dollars it takes to survey and stake a claim.

Because the deposit is mostly on federal land, owned by the Bureau of Land Management and the National Forest Service, successful applicants will essentially lease the right to mine, said Pam Stiles, a BLM land-law examiner in Cheyenne.

The laws regarding claim staking have changed little since 1872, she said.

"It's first come, first served," she said. "If people think it's something major, they'll be out there knocking each other over."

It has been decades since such a scramble for mining claims happened in Colorado - in the 1950s, it was for uranium, Cappa said. In Wyoming, Stiles recalled a bentonite rush in the early 1990s, when miners stood at the edge of the site with picks and shovels, waiting for the opening.

The possibility of a rush motivated Hausel to make the opal-location announcement at a scheduled time, to put everyone on the same playing field, he said.