Lepidocrocite (γ-FeO(OH)), also called esmeraldite or hydrohematite, is an iron oxide-hydroxide. Lepidocrocite has an orthorhombic , a hardness of 5, specific gravity and a yellow-brown streak. It is red to reddish brown and forms when iron underwater. Lepidocrocite is commonly found in the weathering of primary iron minerals and in iron ore inside old steel and water tanks.
The structure of lepidocrocite is similar to the boehmite structure found in bauxite and consists of layered iron(III) oxide octahedra bonded by hydrogen bonding layers. This relatively weakly bonded layering accounts for the scaley habit of the mineral.
It was first described in 1813 from the Zlaté Hory polymetallic ore. The name is from the Greek lipis for scale and krokis for fibre.