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There are numerous locations in the western United States where opal has been found. Some places have even found material with good fire. There never seems to be enough to warrant a mining operation. Spencer, Idaho is an execption to that rule. It is a very small town in Eastern Idaho, about an hour North of Idaho Falls and fifteen minutes South of the Montana border. The town is at 6,000 feet elevation and the mine is at 7,000 feet. Due to very cold winters, snow and mud in the spring, the mining season is about 4 months long (late May to early October). The opal here formed as nodules of silica that filled pockets in a volcanic material similar to Obsidian. Most of the opal has no fire and is called common opal. The fire layers tend to be thin, relatively flat layers in these nodules. A very small amount of opal is found here that will cut solid stones. Nearly all the fire opal must be cut into triplets. Normally this involves a clear top layer and a black bottom layer with a thin slice of opal in the middle. As in most mining operations, there is a lot of marginal quality
material worked for each really good stone that is available. We
have no time or desire to work low quality stones. What we cut or
buy represents the upper 5 to 10% of the available material.
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