Maghemite

a mineral, a magnetic modification of the ferric oxide γ — Fe₂O₃. Generally containing admixtures of FeO and TiO₂, maghemite is unstable in the natural state and is readily converted into stable hematite. It crystallizes in the tetragonal (pseudoisometric) system characterized by a defective spinel structure of the magnetite type. Maghemite has a hardness of 5-6 on Mohs’ scale and a density of 4,700-4,900 kg/m³. It is opaque and has a dark brown color with a steel-like hue. Maghemite occurs in nature only in the form of microscopically fine depositions in magnetite oxidation products and in titanomagnetite (with hematite, iron hydroxides). It is sometimes found in limonite and laterite as the product formed during the surface weathering of minerals containing iron.