Limonite Iron Ore Specimen
Limonite (Hydrated Iron Oxide-Hydroxide mixture) · Mineral Specimen / Iron Ore
Crystal System
Amorphous or pseudo-crystalline, typically massive, botryoidal, reniform, or stalactitic habit
Mineral Group
Oxides and Hydroxides
Chemical Formula
FeO(OH)·nH2O
Formation Process
Sedimentary or weathering (supergene) process resulting from the oxidation and hydration of iron-rich minerals like pyrite, magnetite, and hematite in near-surface environments
About This Crystal
An opaque, heavy, irregularly shaped rough mineral specimen with a rugged, earthy texture. The dominant coloration is a mottled mix of rusty brown, ochre yellow, reddish-brown, and dark brown, indicative of iron oxide staining and weathering. The surface displays pitted, uneven hollows and earthy crusts.
Physical Characteristics
Color ranges from yellowish-brown to dark brown and blackish-brown. Streak is distinctive yellowish-brown or brownish-yellow. Cleavage is absent (massive). Fracture is uneven to earthy. Specific gravity is approximately 2.7 to 4.3 depending on hydration and porosity. Tenacity is brittle to earthy.
Optical Properties
Singly refractive (isotropic) when amorphous, though rarely observed optically as distinct grains. Typically opaque with an earthy to sub-metallic or silky luster.
Hardness & Durability
Origin Region
Found worldwide, notable deposits in the USA, France, Germany, Cuba, and Brazil; forms in weathered zones of iron-bearing rocks
Hardness & Durability
Mohs hardness varies widely from 4 to 5.5 due to variable porosity and hydration states. Low durability for jewelry use due to earthy, friable nature.
Care & Maintenance
Store in a dry environment to prevent further degradation or moisture absorption. Clean gently with a soft brush; avoid harsh chemicals, acids, and prolonged water immersion due to porous nature.
Rarity & Value
Common; widespread globally as a major iron ore and weathering product. Value is generally low, mostly valued by mineral collectors for educational specimens or raw aesthetic forms.
Special Characteristics
Often exhibits a characteristic yellowish-brown streak which distinguishes it from hematite (which has a red streak). Can act as a pseudomorph after other minerals like pyrite.
Lore & History
Historically used as an early natural pigment (ochre) for cave paintings and pottery. In metaphysical lore, it is sometimes associated with grounding, stability, and clearing mental clutter, though these are traditional beliefs with no scientific backing.