Lepidocrocite (γ-FeO(OH)), also called esmeraldite or hydrohematite, is an iron oxide-hydroxide

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): Mi ...

. Lepidocrocite has an orthorhombic

crystal structure In crystallography, crystal structure is a description of ordered arrangement of atoms, ions, or molecules in a crystalline material. Ordered structures occur from intrinsic nature of constituent particles to form symmetric patterns that repeat ...

, a

hardness In materials science, hardness (antonym: softness) is a measure of the resistance to plastic deformation, such as an indentation (over an area) or a scratch (linear), induced mechanically either by Pressing (metalworking), pressing or abrasion ...

of 5,

specific gravity Relative density, also called specific gravity, is a dimensionless quantity defined as the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for solids and liquids is nea ...

of 4, a submetallic luster and a yellow-brown streak. It is red to reddish brown and forms when

iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...

-containing substances rust underwater. Lepidocrocite is commonly found in the weathering of primary iron minerals and in

iron ore Iron ores are rocks and minerals from which metallic iron can be economically extracted. The ores are usually rich in iron oxides and vary in color from dark grey, bright yellow, or deep purple to rusty red. The iron is usually found in the f ...

deposits. It can be seen as rust scale inside old

steel Steel is an alloy of iron and carbon that demonstrates improved mechanical properties compared to the pure form of iron. Due to steel's high Young's modulus, elastic modulus, Yield (engineering), yield strength, Fracture, fracture strength a ...

water pipes and water tanks. The structure of lepidocrocite is similar to the boehmite structure found in

bauxite Bauxite () is a sedimentary rock with a relatively high aluminium content. It is the world's main source of aluminium and gallium. Bauxite consists mostly of the aluminium minerals gibbsite (), boehmite (γ-AlO(OH)), and diaspore (α-AlO(OH) ...

and consists of layered iron(III) oxide octahedra bonded by

hydrogen bonding In chemistry, a hydrogen bond (H-bond) is a specific type of molecular interaction that exhibits partial covalent character and cannot be described as a purely electrostatic force. It occurs when a hydrogen (H) atom, Covalent bond, covalently b ...

via

hydroxide Hydroxide is a diatomic anion with chemical formula OH−. It consists of an oxygen and hydrogen atom held together by a single covalent bond, and carries a negative electric charge. It is an important but usually minor constituent of water. It ...

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 deposit in

Moravia Moravia ( ; ) is a historical region in the eastern Czech Republic, roughly encompassing its territory within the Danube River's drainage basin. It is one of three historical Czech lands, with Bohemia and Czech Silesia. The medieval and early ...

Czech Republic The Czech Republic, also known as Czechia, and historically known as Bohemia, is a landlocked country in Central Europe. The country is bordered by Austria to the south, Germany to the west, Poland to the northeast, and Slovakia to the south ...

. The name is from the Greek ''lipis'' for ''scale'' and ''krokis'' for ''fibre.'' Lepidocrocite crystal structure

References

''Lepidocrocite and Boehmite Structure''
Steven Dutch, 8 March 2002. Hydroxide minerals Iron(III) minerals Orthorhombic minerals Minerals in space group 63 Blendes {{oxide-mineral-stub