Limonite (Geethite in Iron Matrix)
Hydrous Ferric Oxide (mixture of Goethite α-Fe3+O(OH) and other iron oxides) · Mineral Specimen / Industrial Iron Ore
Crystal System
Amorphous or Monoclinic/Orthorhombic (Microcrystalline); Typically occurs in massive, earthy, botryoidal, or stalactitic habits.
Mineral Group
Oxides / Hydroxides
Chemical Formula
FeO(OH)·nH2O
Formation Process
Secondary formation through the chemical weathering of iron-bearing minerals (like pyrite, magnetite, or siderite) or inorganic precipitation in bogs and marine environments.
About This Crystal
An opaque, earthy to sub-metallic mineral showing a range of yellow-brown to ochre and dark brown hues. The specimen exhibits a rough, porous, and uneven surface texture typical of gossan (iron hat) material, with a dull to resinous luster in some areas.
Physical Characteristics
Color: Yellowish brown to dark brown; Streak: Yellowish-brown; Cleavage: None; Fracture: Uneven or earthy; Specific Gravity: 2.7 to 4.3; Non-magnetic (usually); No fluorescence.
Optical Properties
Opaque; Refractive Index: 2.0 to 2.4 (variable due to moisture/impurities); No pleochroism or dispersion visible due to opacity.
Hardness & Durability
Origin Region
Worldwide; Notable deposits in France (Limoges), Brazil, USA (Minnesota, Alabama), and Australia. Found in oxidation zones of iron-rich deposits.
Hardness & Durability
Mohs Hardness: 4.0 to 5.5; Brittle tenacity; Low wearability for jewelry; Sensitive to acids and may lose water content if subjected to intense heat.
Care & Maintenance
Gently dust with a soft brush; avoid water submersion as it can be porous. Keep away from household chemicals and acids. Store in a dry environment to prevent further oxidation or crumbling.
Rarity & Value
Common; Value is generally low for mass specimens, though colorful 'iridescent' limonite or specimens with interesting stalactitic shapes can hold higher collector value.
Special Characteristics
Often forms 'pseudomorphs' (taking the shape of the mineral it replaced, such as pyrite cubes). It is a major component of yellow ochre pigment.
Lore & History
Historically used as an iron ore and a primary source of yellow pigment for cave paintings and pottery since prehistoric times. In traditional lore, it is considered a grounding stone that provides inner strength and stability during periods of transition.