Lepidocrocite is the orthorhombic dimorph of FeO(OH), forming alongside or replacing goethite (the more common variety). It produces distinctive ruby-red translucent micaceous flakes when well-crystallized — a sharp contrast to typical brown-black iron oxide habits.
Properties
- Formula: γ-FeO(OH)
- Crystal system: Orthorhombic
- Hardness: 5
- Color: Ruby-red to reddish-brown, transparent to translucent in flakes
- Streak: Orange to dull yellow
- Luster: Sub-metallic to adamantine
- Cleavage: Perfect on {010} and {001}
- Density: 3.9 – 4.1 g/cm³
Occurrence
Classic localities: Siegerland (Germany), the Ural mines, and Bolivia. Lepidocrocite is also a common inclusion-phase forming “fire quartz” / “iron quartz” — included quartz with ruby-red lepidocrocite plates inside.
Identification
Ruby-red translucent micaceous flakes + perfect basal cleavage + association with goethite. Streak (orange) decisively separates lepidocrocite from hematite (red streak) and goethite (brown streak).
Collector Notes
Lepidocrocite-included quartz from Brazil (Minas Gerais) and Madagascar is a popular gem material. Pure crystallized lepidocrocite plates remain scarce.
Found at these Localities
- Siegerland District (西格兰铁矿区)
- Eastern Brazilian Pegmatite Province (巴西东部伟晶岩省)
