Limonite/Goethite
Goethite with amorphous iron hydroxides (Limonite species-group) · Mineral Specimen / Industrial Iron Ore
Crystal System
Orthorhombic (Goethite) but typically presents as amorphous, massive, or botryoidal crusts.
Mineral Group
Oxides / Hydroxides
Chemical Formula
FeO(OH)·nH2O (Variable hydrous iron oxides)
Formation Process
Secondary formation through the weathering and oxidation of iron-rich primary minerals such as pyrite, magnetite, or siderite (supergene enrichment).
About This Crystal
An opaque, earthy to sub-metallic specimen showing a rugged, vuggy, and porous texture. It exhibits a range of ochre, rusty brown, and tan colors with a dull, matte luster. The surface is characterized by irregular pits and encrustations.
Physical Characteristics
Color: Yellowish-brown to dark brown; Streak: Yellowish-brown; Cleavage: None (massive); Fracture: Uneven to earthy; Specific Gravity: 2.7–4.3; Not typically fluorescent.
Optical Properties
Opaque; No observable pleochroism or dispersion in massive form; Luster is primarily dull or earthy.
Hardness & Durability
Origin Region
Worldwide; notably Minas Gerais (Brazil), Cornwall (UK), and the Mesabi Range (USA). Found in gossans and oxidized zones of ore deposits.
Hardness & Durability
Mohs Hardness: 4.0–5.5; Brittle tenacity; Low suitability for jewelry unless stabilized, but durable enough for handling as a specimen.
Care & Maintenance
Avoid acidic cleaners which may dissolve the iron oxides. Clean with a soft, dry brush to remove dust. Keep in a dry environment to prevent further hydration or structural change.
Rarity & Value
Common; Very low monetary value unless exhibiting rare iridescent 'Turgite' coatings or aesthetic botryoidal habits. Primarily valued as iron ore.
Special Characteristics
Porous, 'gossan' texture indicative of the leaching of original sulfide minerals, leaving behind a 'rusty' iron skeleton.
Lore & History
Historically used as an important iron ore and as a natural earth pigment (ochre) in cave paintings and cosmetics by ancient civilizations. Metaphysically associated with grounding and stability.