Limonite with Goethite
Limonite (an amorphous mixture of hydrated iron oxide-hydroxides, primarily Goethite) · Mineral Specimen / Industrial Iron Ore
Crystal System
Amorphous (Limonite) to Orthorhombic (Goethite); commonly found in massive, botryoidal, or earthy habits.
Mineral Group
Oxides / Hydroxides
Chemical Formula
FeO(OH)·nH2O (primarily FeO(OH))
Formation Process
Secondary formation via the chemical weathering of iron-bearing minerals (like pyrite, magnetite, or hematite) in sedimentary or oxidized hydrothermal environments.
About This Crystal
An opaque, earthy to metallic mineral aggregate featuring a dull brownish-black to ochre-yellow color range. Luster varies from sub-metallic on fresh surfaces to dull/earthy in weathered areas, often showing botryoidal or massive textures with orange-brown gossan staining.
Physical Characteristics
Color: Dark brown to yellow-brown; Streak: Yellowish-brown; Cleavage: None (in Limonite) to Perfect on {010} (in Goethite); Fracture: Uneven to conchoidal; Specific Gravity: 2.7–4.3; Fluorescence: None.
Optical Properties
Opaque; Refractive index is approximately 2.26–2.39 (Goethite), but generally non-measurable in massive limonite specimens. Non-pleochroic in massive form.
Hardness & Durability
Origin Region
Globally abundant; notable sources include Minas Gerais, Brazil, and the Lake Superior region, USA, typically in oxidation zones of iron-rich deposits.
Hardness & Durability
Mohs hardness: 4.0–5.5; Brittle tenacity; stable under normal conditions but can dehydrate into hematite if high heat is applied.
Care & Maintenance
Keep dry to prevent further hydration or structural crumbling; clean only with a soft, dry brush. Avoid ultrasonic cleaners and harsh chemicals which may dissolve or discolor the specimen.
Rarity & Value
Common; primarily valued as a geological specimen or as iron ore. High-quality iridescent 'Turgite' varieties or well-formed botryoidal goethite command higher prices among collectors.
Special Characteristics
Often forms 'gossans' or iron caps over ore deposits; can contain 'enhydro' (trapped water) or exhibit iridescence when mixed with hematite layers.
Lore & History
Historically used as a primary source of yellow ochre pigment for cave paintings and dyes. Metaphysically associated with grounding, physical stamina, and protection due to its dense iron content and earthy origin.