Lepidocrocite

Quartz with Lepidocrocite Goboboseb Mountains, Brandberg District, Namibia miniature – 4 x 3 x 2.5 cm © marinmineral.

Chemical Formula: γ-FeO(OH)
Locality: Common world wide.
Name Origin: From the Greek lipis – “scale” and krokis – “fibre.”
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.

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 via hydroxide 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, Czech Republic. The name is from the Greek lipis for scale and krokis for fibre.

History

Discovery date : 1813
Town of Origin : EISENZECHE, EISERFELD, SIEGEN
Country of Origin : ALLEMAGNE

Optical properties

Optical and misc. Properties : Opaque
Refractive Index : from 1,94 to 2,51
Axial angle 2V: 83°

Physical Properties

Cleavage: {010} Perfect
Color:     Red, Yellowish brown, Blackish brown.
Density: 4
Diaphaneity: Opaque
Fracture: Uneven – Flat surfaces (not cleavage) fractured in an uneven pattern.
Hardness: 5 – Apatite
Luminescence: Non-fluorescent.
Luster: Sub Metallic
Streak: dark yellow brown

Photos:

Quartz (Var.: Amethyst), Lepidocrocite Locality: Huaron Mining District, San Jose de Huayllay District, Cerro de Pasco, Daniel Alcides Carrión Province, Pasco Department, Peru Dimensions: 11.5 cm x 9.5 cm x 4.7 cm Photo Copyright © Rob Lavinsky & irocks
Lepidocrocite in Quartz
Clara Mine, Rankach valley, Oberwolfach, Wolfach, Black Forest, Baden-Württemberg, Germany © Stephan Wolfsried
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