Limonite after Pyrite (Gozan / Iron Hat)
Limonite (pseudomorph after Pyrite) · Mineral Specimen / Collector Mineral
Crystal System
Orthorhombic (Limonite is amorphous or microcrystalline; structure shown is usually Cubic inherited from Pyrite)
Mineral Group
Oxides / Hydroxides
Chemical Formula
FeO(OH)·nH2O
Formation Process
Secondary formation via oxidation and weathering of primary iron sulfides (Pyrite) in the presence of water at low temperatures (Gossan formation).
About This Crystal
An opaque, earthy to metallic specimen with a deep reddish-brown to ochre color. It displays a granular, microcrystalline surface with visible pits and an uneven, earthy luster.
Physical Characteristics
Color: Reddish-brown; Streak: Yellowish-brown; Cleavage: None; Fracture: Uneven/Earthy; Specific Gravity: 2.7 - 4.3; Fluorescence: Typically none.
Optical Properties
Opaque; Non-refractive in massive form; lacks pleochroism or dispersion in this earthy habit.
Hardness & Durability
Origin Region
Worldwide; notable sources in Morocco, Spain (Rio Tinto), and USA (Utah, Arizona). Found in the oxidation zones of ore deposits.
Hardness & Durability
Mohs Hardness: 4 - 5.5; Brittle and prone to crumbling if heavily weathered or porous.
Care & Maintenance
Keep dry; avoid acids. Clean with a soft dry brush. Do not use ultrasonic cleaners as it may cause the specimen to disintegrate.
Rarity & Value
Common; value depends on the preservation of the original crystal 'pseudomorph' shape. Typically low to moderate price range.
Special Characteristics
Pseudomorphism: It takes the external shape of the pyrite crystals it replaced. May contain 'phantom' remnants of the original sulfide.
Lore & History
Historically used as an iron ore and pigment (ochre). In folklore, it is often associated with grounding and physical endurance due to its heavy iron content.