Staurolite is hydrous iron magnesium aluminum silicate. It occurs with garnet, tourmaline, and kyanite or sillimanite in mica schists and gneisses and other metamorphosed aluminum-rich rocks. Staurolite is reddish-brown or yellowish-brown, or nearly black, and normally occurs as prisms which are hexagonal or diamond-shaped in section. Staurolite is named from the Greek stauros, “cross” and lithos “stone”, for its cross-like twinned form. These cross-shaped crystals are frequently set in silver for use in religious jewelry.