lepidocrocite

{{Infobox mineral | name = Lepidocrocite | boxwidth = | boxbgcolor = | image = Mineraly.sk - lepidokrokit.jpg | imagesize = 260px | alt = | caption = A sample of lepidocrocite | category = Oxide minerals | formula = γ-FeO(OH) | IMAsymbol = Lpc | molweight = 88.85 g/mol | strunz = 4.FE.15 | dana = | system = Orthorhombic | class = Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m) | symmetry = Cmcm | unit cell = a = 3.88, b = 12.54 c = 3.07 [Å]; Z = 4 | color = Ruby-red to reddish brown; light reddish to red-orange in transmitted light; gray-white in reflected light | colour = | habit = Flattened scales aggregated into plumose groups and rosettes; massive, bladed to fibrous or micaceous | twinning = | cleavage = {010} Perfect | fracture = | tenacity = | mohs = 5 | luster = sub metallic | streak = Dull orange | diaphaneity = Transparent | gravity = 4 | density = | polish = | opticalprop = Biaxial (−) | refractive = nα = 1.940 nβ = 2.200 nγ = 2.510 | birefringence = δ = 0.570 | pleochroism = Strong; X = colorless to yellow; Y = orange, yellow, dark red-orange; Z = orange, yellow, darker red-orange | 2V = Measured: 83° | dispersion = | extinction = | length fast/slow = | fluorescence = | absorption = | melt = | fusibility = | diagnostic = | solubility = | impurities = | alteration = | other = | prop1 = | prop1text = | references = }}

Lepidocrocite (γ-FeO(OH)), also called esmeraldite or hydrohematite, is an iron oxide-hydroxide mineral. Lepidocrocite has an orthorhombic crystal structure, a hardness of 5, specific gravity of 4, a submetallic luster and a yellow-brown streak. It is red to reddish brown and forms when iron-containing substances rust underwater. Lepidocrocite is commonly found in the weathering of primary iron minerals and in iron ore deposits. It can be seen as rust scale inside old steel water pipes and water tanks.