mineral
Limonite (Iron Ore Congcretion)
Limonite (a mixture of hydrated iron(III) oxide-hydroxides, FeO(OH)·nH2O)
AI-generated identification · may be incorrectHardness: 4-5.5 (variable); Color: Dark brown to yellowish-brown; Luster: Dull, earthy; Crystal structure: Amorphous; Cleavage: None; Specific gravity: 2.7-4.3
- Hardness
- 4-5
- Color
- Dark brown to yellowish-brown
- Luster
- Dull, earthy
Identified More mineral →
Explore Limonite (Iron Ore Congcretion) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 4-5.5 (variable); Color: Dark brown to yellowish-brown; Luster: Dull, earthy; Crystal structure: Amorphous; Cleavage: None; Specific gravity: 2.7-4.3
Formation & geological history
Formed as a secondary material through the oxidation or chemical weathering of iron-rich minerals. Often found as nodules or concretions in sedimentary layers or bog deposits.
Uses & applications
Major historical source of iron ore (bog iron); used today as a natural earth pigment (yellow ochre) and in soil conditioning.
Geological facts
Limonite is not a 'true' mineral but a mineraloid consisting of varying proportions of goethite and other iron oxides. It has been used as a pigment by humans for over 30,000 years in cave paintings.
Field identification & locations
Identify by its yellowish-brown streak on a porcelain plate and its high weight relative to its size. Commonly found in swamps (bog iron) or as 'rust' coatings on other rocks.
