Limonite and Goethite Pseudo-crystal
Goethite-Limonite mixture (Iron Oxyhydroxide) · Mineral Specimen / Industrial Iron Ore
Crystal System
Orthorhombic (as Goethite); typically amorphous or cryptocrystalline in Limonite forms
Mineral Group
Oxides / Hydroxides (Iron Hydroxides)
Chemical Formula
FeO(OH)·nH2O (Variable moisture content)
Formation Process
Sedimentary and Secondary; forms through the chemical weathering of iron-rich precursor minerals like pyrite and magnetite
About This Crystal
Earthym, porous, and aggregate appearance with an ochre to rust-brown color. Features a dull to earthy luster with micro-crystalline sparkles under direct light suggesting goethite clusters.
Physical Characteristics
Yellow-brown to orange-brown body color; yellow-brown streak; no cleavage; uneven or subconchoidal fracture; specific gravity 2.7–4.3; non-magnetic generally.
Optical Properties
Generally opaque; index of refraction is high at 2.2-2.5 but not measurable in earthy aggregates; no pleochroism visible in massive form.
Hardness & Durability
Origin Region
Found globally; notable specimens from Iron Quadrangle, Brazil and the Lake Superior region, USA
Hardness & Durability
Mohs hardness 4.0 - 5.5; brittle and often crumbly if high in limonite content; poor durability for jewelry.
Care & Maintenance
Keep dry as it is porous; clean only with soft brushes; avoid chemical solvents and ultrasonic cleaners; store away from moisture to prevent further oxidation.
Rarity & Value
Very common; low commercial value for small specimens; primarily valued as an industrial source of iron or as a pigment (Ochre).
Special Characteristics
Porous, cellular structure known as 'Gossan'; often displays a shimmering drusy surface of micro-crystals in cracks.
Lore & History
Historically used as the primary pigment for cave paintings; culturally associated with 'grounding' and endurance in traditional lore.