Bauxite, known mostly as aluminium ore; is a naturally occurring, heterogeneous material composed primarily of one or more aluminium hydroxide minerals, including the trihydrate gibbsites, the monohydrate polymorphs boehmite and diaspore plus various mixtures of silica, hematite (iron oxides), siderite (iron carbonates) and other impurities in trace amounts. Most bauxite deposits contain rutile, anatase, zircon and other minerals.