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Sapphire from the Rock Creek Area (Gem Mountain) , Montana

Precambrian and Tertiary deposits around Gem Mountain have been eroded to release and bury the sapphire crystals under layers of gravel. The gravels and sands that contain the sapphire consist of quartz, sandstone, chert, dolostone, mafic volcanics and intrusives, and andesite and rhyolitic rock fragments. Sapphire was first discovered in Montana in the late 1800's by gold miners working the alluvial gravels of the Missouri River near Helena. In 1892 gold prospectors discovered the Gem Mountain sapphire deposit; one of the largest sapphire deposits in the world. The famous Sapphire and Anaconda Gulches at Gem Mountain were so rich they were mined exclusively for gemstones. Since 1893 this mine has produced a reported 180 million carats of sapphire.

Sapphires were mined at Gem Mountain continuously from the turn of the century until the second world war. It wasn't until modern heat treatment processes evolved that Montana sapphire production skyrocketed. In 1991 a young state senator from Minnesota, Greg Dahl, began acquiring mineral rights in the Rock Creek area. In 1994 he purchased the Gem Mountain sapphire deposit. In 1994 Dahl's company, American Gem Corporation, went public. Since then the corporation has done a great deal of discovery work on their properties, they have completed construction of a new plant and mine on the Anaconda Bench on Gem Mountain, and have pursued an aggressive expansion plan for production, cutting, and sale of fine sapphires.

For many years portions of the Gem Mountain sapphire deposit were open to amateur collectors on a fee basis (At one time it cost $60 per person per day!). As of 2012 Gem Mountain was still open to amature "miners" who could purchase buckets of sapphire-containing concentrate to be washed and sorted on site. The status of collectng in this area is continuously changing. Those interested in trying their hand at sapphire mining should contact the Gem Mountain operators, or the local chamber of commerce.

The gemstones from this location are relatively small, but their color and clarity are extremely fine. Colors include red, orange, yellow, pink, green, blue, and many combinations of those colors. Many crystals that do not naturally possess good color or clarity are heat treated under carefully controlled conditions to improve the appearance of the finished gemstones.