Limonite with Quartz and Hematite
Limonite (amorphous mixture of Hydrated Iron Oxides) on Quartz (Silicon Dioxide) · Mineral Specimen / Common Rock-Forming Minerals
Crystal System
Amorphous to Orthorhombic (Goethite in Limonite); Quartz is Trigonal. Habit is massive, earthy, and microcrystalline.
Mineral Group
Oxides / Hydroxides and Silicates (Tectosilicates)
Chemical Formula
FeO(OH)·nH2O (Limonite) + SiO2 (Quartz) + Fe2O3 (Hematite)
Formation Process
Secondary formation via weathering and oxidation of iron-rich minerals (like Pyrite or Magnetite) in a sedimentary or hydrothermal environment.
About This Crystal
An opaque, earthy to sub-metallic mass showing yellowish-brown to dark chocolate brown iron staining. White crystalline patches of quartz are visible in the matrix.
Physical Characteristics
Color: Yellow-brown to black-brown; Streak: Yellow-brown/ochre; Cleavage: None; Fracture: Earthy or uneven; Specific Gravity: 2.7 - 4.3; Non-fluorescent.
Optical Properties
Opaque (Limonite) to Transparent (Quartz). No significant pleochroism or dispersion in this earthy form; dull to vitreous luster.
Hardness & Durability
Origin Region
Global occurrence; common in oxidized zones of iron-rich ore deposits (gossans) and sedimentary bog iron.
Hardness & Durability
Mohs hardness 4–5.5 (Limonite) and 7 (Quartz). Brittle tenacity; generally stable but can be porous.
Care & Maintenance
Keep dry to prevent further oxidation; clean with a soft brush. Avoid acidic cleaners which may dissolve iron oxides.
Rarity & Value
Very common; low commercial value as a gemstone but high historical value as an iron ore (ochre).
Special Characteristics
Pseudomorphism (often replacing pyrite crystals) and use as a natural pigment (ochre). Presence of 'gossan' texture indicating deeper ore bodies.
Lore & History
Used since prehistoric times as a pigment for cave paintings; historically significant as a primary iron source for early civilizations (Iron Age).