Oct 23

Gems: Every Color of the Rainbow

by Diane Cochran

At Gem Mountain Mine near Philipsburg, anyone can be a miner for a day and a successful one at that. Tweezers, plus a screen and some water, are the tools of the trade.

Guests can pay $20 for a bucket filled with 2 1/2 gallons of gravelly dirt and up to 20 karats of sapphires. The sapphires occur naturally here, so there is no guarantee how many will surface in any given bucket or what size or color they will be.

But there are so many of the stones in the ground that everyone is certain to discover some.

“People found 500 stones last year that were three karats or greater,” said Chris Cooney, who has owned the mine for the past 13 years. “Gem Mountain is the quiet giant of sapphire mines.”

The alluvial sapphire deposit stretches over six square miles of the Sapphire Mountains southwest of Philipsburg.

“The sapphires are about 50 million years old,” Cooney said. “Volcanic activity brought them to the surface.”

They rest within the frost zone, or no more than about four feet deep. Cooney uses a loader to scoop up sapphire-laced dirt at a rate of an acre a year. He washes it to remove big rocks and clay. Then it goes into buckets for sale to the public.

In addition to offering single buckets for $20, the mine has a “lucky seven” deal, which earns customers who buy six buckets a seventh one for free, and a “dirty dozen” deal, or 12 buckets for the price of ten.

It can take a couple of hours to work through one bucket. You start by ladling scoops of dirt onto a screen and washing it by hand in a water trough. Just the right washing technique, which Gem Mountain employees will demonstrate for you, separates the sapphires and collects them at the center of the screen.

When your screen is clean, you dump out the contents and go to work with your tweezers. On a sunny day, the wet sapphires glint in the light and are fairly easy to spot.

“Most of the stones are a light pastel,” Cooney said. “They come in every color of the rainbow depending on what metal impurities are in the stone.”

Pale green is the most common color, but they can be pink, red, orange, yellow, or purple, among other shades. Heat-treating, which Gem Mountain offers, intensifies the color. The mine also offers faceting, or cutting the stones for jewelry.

Sapphires were first mined at Gem Mountain in the 1890s. Back then, the gems were used as instrument bearings in watches. Most of them were sold to jewelers in Switzerland, although some large specimens were displayed at the World’s Fair, Cooney said. The mine began offering its dirt to the public in the 1960s.

Gem Mountain Mine is open from Memorial Day weekend to the first weekend of October. For information on how to get there or to order mine dirt, visit www.gemmountainmt.com.

Two kinds of sapphires are found in Montana: Montana sapphires and Yogo sapphires.

Montana sapphires, which are mined at Gem Mountain Mine near Philipsburg, are found in alluvial deposits and require heat treating to gain jewelry-quality color.

Yogo sapphires are mined from a hardrock vein near Lewistown. They are much harder to mine but do not require heat treating before being sold as jewels. They are brilliant in natural and artificial light.

“Yogos are a superb cornflower blue,” said Lee Woodward, a geologist who recently co-authored a book about Yogos called “Yogo Sapphire Mine: The History of World Class Gem.”

Woodward called the Yogo deposit in Central Montana world class.

“Nearly every woman in town has a Yogo sapphire, and, if she doesn’t, she wishes she did,” he said.

Dale Pfau, owner of Don’s Store in Lewistown, said demand always outstrips supply for Yogos.

“We have people come from all over theworld to buy them,” he said.

 

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