Limonite with Goethite on Gossan Matrix
Limonite (an amorphous mixture of hydrated iron oxides, primarily Goethite α-Fe3+O(OH)) · Mineral Specimen / Industrial Iron Ore
Crystal System
Amorphous / Orthorhombic (as Goethite); typically displays massive, earthy, or botryoidal habits
Mineral Group
Oxides and Hydroxides
Chemical Formula
FeO(OH)·nH2O (variable mixture often containing Goethite, Lepidocrocite, and Jarosite)
Formation Process
Secondary formation via chemical weathering and oxidation of iron-bearing sulfide minerals (like Pyrite) in the presence of water and oxygen
About This Crystal
An opaque, earthy to sub-metallic mineral specimen. It features a range of colors from dark brown and rusty orange to yellowish-tan. The surface is rugose, porous, and displays a dull, earthy luster with some darker, more compact areas suggesting concentrated iron oxides.
Physical Characteristics
Color: Yellowish-brown to dark brown; Streak: Yellow-brown; Luster: Dull to earthy; Fracture: Uneven or earthy; Specific Gravity: 2.7–4.3 (variable); Magnetism: Usually non-magnetic but may contain trace Magnetite.
Optical Properties
Opaque; No visible light transmission; Refractive index is not applicable for this massive material; No pleochroism or dispersion visible.
Hardness & Durability
Origin Region
Global; typically found in the weathered 'gossan' zones of sulfide ore deposits in regions like Australia, Brazil, and the USA
Hardness & Durability
Mohs hardness ranges from 4 to 5.5; Brittle and often friable (crumbling easily if earthy); Low durability for jewelry use.
Care & Maintenance
Keep dry to prevent further oxidation or crumbling; clean with soft brushes only; avoid chemical cleaners or ultrasonic baths which can dissolve or break the porous matrix.
Rarity & Value
Common; low monetary value as a specimen unless displaying unique iridescent 'turgite' coatings or mammillary forms; primarily valued as iron ore.
Special Characteristics
Occurs as a pseudomorph after other minerals; the specimen shows a 'gossan' texture, which is a geological indicator of potential underlying metal ores (ore hat).
Lore & History
Historically used as 'yellow ochre' pigment for cave paintings and pottery. In traditional lore, it is considered a stone of grounding and endurance, though these represent cultural beliefs rather than scientific facts.