sillimanite

A usually white, hard mineral, Al₂SiO₅, occurring in highly metamorphosed rock as long, slender, fibrous crystals.

A silicate of aluminium (Al₂SiO₅), having the same composition as andalusite and cyanite.

Same as fibrolite.

A fibrous neosilicate mineral, polymorphic with andalusite and kyanite, with the chemical formula Al2SiO5.