Idaho State Gemstone or Gem

Star Garnet

(Quartz)

Adopted on February 25, 1967.

Adopted by the 1967 legislature, the Idaho Star Garnet,  Quartz, is known worldwide by collectors. Garnets are complex silicates, related to Quartz, and found almost exclusively in Idaho in Latah and Benewah counties. Star Garnets are a natural stone, not synthetically produced. Star Garnet, Idaho's state gem, comes from only two places in the world: India and Northern Idaho near St. Maries. The Idaho State Forestry Service sponsors a fee digging site at Emerald Creek, in the St. Joe National Forest, off State Highway 3, about 10 miles east of Clarkia, in Latah County.

Alluvial deposits of almandite garnet were discovered in the early 1880's near Fernwood in Benewah County, but commercial gem and industrial mining did not start until the early 1940's. The deposits are on Emerald, Carpenter, and Meadow Creeks about 6.4 km from a mica-garnet schist formation. The garnet-bearing gravels are about 1 m to about 1.2 m thick and contain 8% to 15% garnet. These deposits are the basis of the largest industrial garnet mine in the nation and also produce gem garnet. Additionally, star garnets are produced from the placers of Purdue Creek in Latah County.

Star Garnets are more rare than either Star Rubies or Star Sapphires. Normally the star in the Idaho Garnet has four rays, but occasionally one has six rays as in a Sapphire. The color is usually dark purple or plum and the star seems to glide or float across the dark surface. The star is caused by intrusions of the mineral rutile.

Garnet forms from a whole family of minerals: aluminum, calcium, chromium, silicon, oxygen, magnesium, manganese, iron, and vanadium, into several classifications of garnet. The Almandine or almandite garnet when included with pyroxene or amphibole creates a chatoyance that yields four and occasionally six ray stars. Idaho's deposits also are the only ones in the world, besides India, that produces significant amounts of star garnets. These Almandine or almandite garnets are translucent, purplish-red stones that show four- or six-ray stars when cabochon cut, or are transparent, deep red stones that can be faceted. The asterism is the result of silky rutile inclusions. Star garnet can be differentiated from other garnet by the silk inclusions. There is not much garnet of this quality left In Idaho or India either.

Gem-quality garnets also are produced commercially from an area of the Little North Fork and North Fork of the Clearwater River in Clearwater County. They range from purplish rose-red to a highly prized "special pink." Gem-quality garnets occur at a number of other locations in Idaho and are periodically mined by hobbyists or professional collectors for the gemstone market.

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