n.
or cyanite or disthene
Silicate mineral , one of several phases in the aluminum silicate (Al 2 SiO 5 ) system.
Its colour ranges from gray-green to black or blue, with blue and blue-gray being most common. It occurs in Switzerland, Italy, the Ural Mountains, and New England (U.S.). Kyanite is a raw material in the manufacture of spark plugs. A clear, deep-blue variety is sometimes cut as a gemstone.