Idaho is known as the "Gem State" because it contains 72 different kinds of precious and semi-precious stones. Idaho gems can be found throughout the state, particularly in mining sites and stream beds. The only other location on the planet which has a greater variety of gems is Africa. Idaho's state gem is the star garnet. Throughout the state there are numerous and popular gem-hunting spots where enthusiasts can find deposits of corundum, jasper, agate, opal, garnet, topaz and zircon.
Explore old mine dumps where weathering and erosion expose mineral specimens, as these are good collecting spots. Statewide, the mineral corundum occurs in a variety of colors. These include the transparent red corundum, the gemstone ruby, and the blue variety, the gemstone sapphire. Corundum concentrates in placer deposits and is recovered using a screen in the same way as placer gold. Garnets also occur throughout the state in a variety of rock types.
Outside St. Maries, on the East Fork of Emerald Creek in the Panhandle National Forest, gem-quality almandite garnets are found in the placer gravel of the stream bed. These garnets range from purple to red in color and are significant for their stars, called star garnets. Most collectors will actually dig into the bedrock and use screens to recover these gems. To collect star garnets in the area, you must pay a small permit fee to the U.S. Forest Service. The gravel bars along Rhodes and Orofino Creeks in Clearwater County, near Pierce to the south, also contain deposits of corundum.
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You'll find corundum placer deposits in the Stanley Basin of Custer County, and in the Gold Fork tributary of the Payette River in Valley County. Between McCall and New Meadows on the headwaters of Goose Creek in the east-central part of the state there is also a corundum site, known as Rocky Flat. Look for agate nodules, with colors ranging from white, grey, to blue-grey, along Road Creek, a tributary of the East Fork of the Salmon River between Sawtooth National Recreation Area and Sawtooth National Forest.
Fire opals draw rock hounds to Squaw Butte, 50 miles north of the town of Emmett in Gem County, where cherry and salmon pink opals can be found. The best known jasper in Idaho is the "Bruneau jasper," a red and green gem-quality stone found in Bruneau Canyon located 50 miles south of the town of Bruneau in the Owyhee County.
The Spencer opal deposit is located 5 miles northeast of the town of Spencer, near the Montana border. Many opal deposits are located on the south side of Opal Mountain, but some are covered under patented or unpatented mining claims. One of the best deposits in the area is the Deer Hunt Mine, which is open for digging by rock hounds for a set price per pound.