Kyanite Statistics and Information

By National Minerals Information Center

Statistics and information on the worldwide supply of, demand for, and flow of the mineral commodities kyanite, andalusite, and sillimanite

Kyanite, andalusite, and sillimanite are anhydrous aluminosilicate minerals that have the same chemical formula, Al₂SiO₅, but differ in crystal structure and physical properties. When calcined at high temperatures (around 1,350° C to 1,380° C for kyanite and slightly higher for andalusite and sillimanite), these minerals are converted to mullite, 3Al₂O₃·2SiO₂, and silica, SiO₂, which are refractory materials. In the conversion to mullite, 1 metric ton (t) of mineral concentrate yields about 0.88 t of mullite. Synthetic mullite is made by heating mixtures of alumina and silica or bauxite and kaolin at around 1,550° C to 2,000° C. Refractories are heat-resistant materials used in high-temperature applications such as furnaces, boilers, ladles, and kilns, in the metallurgical, glass, chemical, cement, and other industries.

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