Garnet has been used as a gemstone for centuries. However, garnet's angular fractures, relatively high hardness and specific gravity, being chemically inert and nontoxic and free of crystalline silica, and its ability to be recycled make garnet ideal for many industrial applications. Garnet is the general name given to a group of complex silicate minerals. All have isometric crystal structure and similar properties and chemical compositions. In 2004, U.S. production of crude garnet concentrate for industrial use was estimated to be 28.4 kt (26,400 st) valued at about 3.05 million dollars. This was a 3-percent decrease in production and a decrease of about 4 percent in value compared with 29.2 kt (32,200 st) valued at 3.16 million dollars in 2003. Refined garnet material sold or used was 30.4 kt (33,500 st) valued at 10 million dollars. This was an 8-percent decrease in quantity and a decrease of almost 8 percent in value compared with the 2003 levels. Garnet for industrial use was mined in 2004 by three firms, one in Idaho and two in New York. The only Montana garnet producer reported no production for the year and was in foreclosure at the end of the year. The majority of industrial-grade garnet mined in the United States is almandite (iron-aluminum silicate). Some andradite (calcium-iron silicate) also is mined domestically for industrial uses.
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