Limonite with Goethite inclusions
Limonite (an amorphous mineraloid mixture of hydrated iron oxides) · Mineral Specimen / Industrial Iron Ore
Crystal System
Amorphous/Microcrystalline; often occurs in botryoidal, stalactitic, or massive habits within an earthy matrix.
Mineral Group
Oxides and Hydroxides
Chemical Formula
FeO(OH)·nH2O (Major components: Goethite, Akaganeite, Lepidocrocite, and Jarosite)
Formation Process
Secondary formation; occurs through the oxidation and hydration of iron-rich minerals (like pyrite or magnetite) in sedentary or weathering environments.
About This Crystal
An earthy, yellowish-brown to dark brown crust with visible metallic to sub-metallic flecks. The surface appears matte and porous in some areas, while other spots show a slight glimmer from microcrystalline inclusions.
Physical Characteristics
Color: Yellow-brown to blackish; Streak: Yellowish-brown; Cleavage: None; Fracture: Uneven to earthy; Specific Gravity: 2.7–4.3; Fluorescence: Generally none.
Optical Properties
Refractive Index: 2.0 to 2.4 (variable); Opaque; Luster ranges from earthy/dull to sub-metallic; No pleochroism due to being opaque.
Hardness & Durability
Origin Region
Global; notably from the Iron Quadrangle (Brazil), Minnesota (USA), and various localities in France and Germany.
Hardness & Durability
Mohs hardness: 4.0 to 5.5 (highly variable depending on water content); Brittle; Low wearability for jewelry.
Care & Maintenance
Avoid acidic cleaners as they can dissolve iron oxides; clean with a soft dry brush; store in a low-humidity environment to prevent further oxidation or crumbling.
Rarity & Value
Common; very low value as a single specimen unless it is a high-quality pseudomorph; primarily valued as a source of iron ore.
Special Characteristics
Frequently forms pseudomorphs after other minerals like pyrite, retaining the original crystal shape (cubes) but changing the chemical composition.
Lore & History
Historically used as an ochre pigment for cave paintings; in folklore, it is often called 'Yellow Ochre' or 'Brown Hematite' and is traditionally associated with grounding and physical protection.