Limonite with Goethite inclusions
Hydrated Iron Oxide (Limonite) with Alpha-FeO(OH) (Goethite) · Mineral Specimen and Pigment Source
Crystal System
Amorphous or Cryptocrystalline (Limonite); Orthorhombic (Goethite) with massive or earthy habit
Mineral Group
Oxides and Hydroxides
Chemical Formula
FeO(OH)·nH2O (Generic formula for Limonite)
Formation Process
Sedimentary and secondary formation; typically forms in the oxidation zones of iron-rich mineral deposits through weathering
About This Crystal
Earthly, dull appearance with a rusty-brown to yellowish body color. The specimen is opaque with a predominantly earthy to sub-metallic luster on fresh breaks. It shows a rugged, granular surface texture with dark greyish-black zones indicating higher concentrations of crystalline goethite.
Physical Characteristics
Color: Yellowish-brown to dark brown; Streak: Yellowish-brown; Cleavage: None (massive); Fracture: Uneven to conchoidal; Specific Gravity: 2.7 to 4.3; Fluorescence: Usually none
Optical Properties
Opaque; No light transmission so refractive index is not applicable for field identification; non-pleochroic in massive form
Hardness & Durability
Origin Region
Globally distributed; notable sources in Minas Gerais (Brazil), Cornwall (UK), and Iron Belt regions of the USA
Hardness & Durability
Mohs hardness: 4 to 5.5; Brittle tenacity; stable under normal conditions but can dehydrate into hematite if high heat is applied
Care & Maintenance
Dust with a soft brush; avoid water as it can promote further oxidation or crumbling in earthy specimens; store in a dry environment to prevent mechanical degradation
Rarity & Value
Common; low monetary value but high industrial value as an iron ore; specimens are valued based on historical context or as part of mineralogical suites
Special Characteristics
Shows characteristic ochre coloration; may contain pseudomorphs after other iron-bearing minerals like pyrite
Lore & History
Historically used as 'Yellow Ochre' pigment for cave paintings and pottery; traditionally associated with grounding and physical endurance in various folklore traditions