Limonite with Goethite (Bog Iron/Iron Nodular Ore)
Limonite (an amorphous mixture of hydrated iron oxides, primarily Goethite) · Mineral Specimen / Industrial Iron Ore
Crystal System
Amorphous or Orthorhombic (Goethite crystals are orthorhombic); Habit is typically massive, botryoidal, or earthy.
Mineral Group
Oxides and Hydroxides
Chemical Formula
FeO(OH)·nH2O
Formation Process
Secondary formation via chemical weathering of iron-rich minerals or biogenic precipitation in swampy/oxygen-poor environments (Sedimentary/Hydrothermal weathering).
About This Crystal
Large, heavy massive specimen with a botryoidal to bumpy surface. It exhibits a dark metallic charcoal to black exterior with significant ochre-orange to rusty brown oxidation. Opaque with a dull to sub-metallic luster.
Physical Characteristics
Color: Dark brown to black with yellow-brown streaks. Streak: Yellowish-brown. Fracture: Uneven to conchoidal. Specific Gravity: 2.7–4.3. Notable for its weight and lack of magnetism (unless containing Magnetite).
Optical Properties
Opaque; No refractive index measurable by standard gemstone methods. No pleochroism or dispersion. Subject to 'luster' variation from earthy to sub-metallic.
Hardness & Durability
Origin Region
Worldwide; often found in bog deposits, gossans (weathered ore caps), and sedimentary iron formations.
Hardness & Durability
Mohs Hardness: 4 to 5.5. Brittle tenacity. Generally stable but can be porous and susceptible to further oxidation if kept in high humidity.
Care & Maintenance
Keep dry to prevent further oxidation (rusting). Clean with a soft dry brush; avoid water or chemicals which can penetrate the porous matrix. Store separately to prevent scratching softer surfaces.
Rarity & Value
Common; Value is generally low as a collector specimen unless displaying high iridescent 'Turgite' colors or distinct botryoidal forms. Primarily valued as iron ore.
Special Characteristics
Features visible white marine encrustations (likely worm tubes or calcite mineral deposits), suggesting a possible marine or coastal origin for this specific piece.
Lore & History
Historically used as a primary source of iron for over two millennia (Bog Iron). Used as a pigment (Ochre) by ancient civilizations for cave paintings. Metaphysically associated with grounding and protection.