The picture on the right is a chunk of Idaho opal rough. If you look close. The white opal in the foreground has many small layers. Most of these layers are just plain white opal. However a few of the layers will be a very high grade opal, called black crystal. Black crystal opal is a very clear opal, with many different colors flashing through it. Black crystal is transparent or nearly transparent and should not be confused with true black opal.
Idaho opal is very much like Australian boulder opal. Boulder opal is also a black crystal type of opal. Bolder Opal formed natural doublets by filling cracks in a dark host rock called ironstone. The ironstone is cut away to expose a thin layer of opal and some of the ironstone is left for a backing. Unlike Australia's ironstone base, Idaho's white opal base, is too unstable to be left as backing.
So the white opal is cut away to expose the fire layer. A black basalt backing is then epoxied to the exposed precious opal. The white opal on the other side is then removed. Now the opal has a dark background and begins to look like an Australian boulder opal. The process is then taken one step further. A crystal or quartz cap is epoxied on top. This protects the brittle precious opal. The cap also gives the fire in the Idaho Opal a little more depth, than the fire in an Australian bolder opal. These three layers are called an opal triplet.
The primary formation of the mine is a rhyolite and obsidian flow, full of gas pockets. The opal solution, a silica, was a secondary deposit caused by geyser activity, which settled in the gas pockets. As a result of many eruptions over a long period of time, the opal lays in layers. Most of the layers are very thin. Occasionally one of the layers would contain precious opal. These precious opal layers make some of the most brilliant and beautiful triplet opal in the world.
Spencer Opal is found in southeastern Idaho near Duboise. The Spencer Opal mine is located about 70 miles West of Yellowstone National Park. The mine was discovered by hunters in 1948, and filed on as a mining claim in 1952.
New Kids On the Block
Spencer Opal Mines is no longer the only opal producing mine In Idaho. The new kids on the block. Are Bob and Susan Thompson. They purchased their opal mining claim in 1991. After
a couple of years of hard work developing the mine, they found an incredible amount of gem grade opal to work with. They then began, by supplying their precious opal to jewelry stores and custom goldsmiths, like ourselves. Starting in Idaho and surrounding states. Since then they opened their first retail store in Dubois, Idaho. Just off Interstate 15, where the tourists stop to rest and gas up.
After that they bought the old general store in Spencer, just 13 miles north of Dubois off Interstate 15. If you find yourself in the area, stop in at one of their stores. You have to see this amazing Gem first hand. Our pictures just can't show the true beauty of these stones. Their store name is "Opal MT. Mine". Since the store is also the old Texaco gas station, they inherited one gas pump, which is very popular in this desolate area of the country. They tell everyone they are the only jewelry store in the world with a gas pump. You can find more information about Bob and Susan on their website. We have a link to their site in our useful links pages under the heading (Gemstone Only Sites)