Sillimanite << SIHL uh muh nyt >> is a mineral that is brown, pale green, or white, and has a glassy luster. It belongs to the large class of minerals known as silicates (see Silicate). Its chemical formula is Al2SiO5. Sillimanite is sometimes called fibrolite because its crystals commonly are fiberlike. Sillimanite is found in Brazil, central Europe, Myanmar, Sri Lanka, and the United States. It occurs in metamorphic rock (rock changed by heat or by heat and pressure). See Metamorphic rock.
