sedimentary

Bog Iron (Limonite)

Limonite (Hydrated iron(III) oxide-hydroxide, FeO(OH)·nH2O)

AI-generated identification · may be incorrect

Hardness: 4.0-5.5; Color: Dark brown to yellowish-brown; Luster: Dull to earthy; Crystal Structure: Amorphous; Cleavage: None; Specific Gravity: 2.7-4.3

Hardness: 4
Color: Dark brown to yellowish-brown
Luster: Dull to earthy

Identified June 8, 2026More sedimentary →

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Physical properties

Hardness: 4.0-5.5; Color: Dark brown to yellowish-brown; Luster: Dull to earthy; Crystal Structure: Amorphous; Cleavage: None; Specific Gravity: 2.7-4.3

Formation & geological history

Formed through the chemical or biochemical precipitation of iron oxides from groundwater or stagnant water in swamps, bogs, and wetlands. It is often Holocene in age though can be older.

Uses & applications

Historically used as a major source of iron ore for early metalworking; currently used as a mineral pigment (ochre) and in soil conditioning.

Geological facts

Bog iron was the primary source of iron for Vikings and early American settlers before high-grade hematite and magnetite mines were developed. It is renewable on a human timescale, as it can reform in a bog after being harvested.

Field identification & locations

Identify by its brown-orange streak, earthy texture, and association with wetlands. Common in glaciated areas of Northern Europe and North America. Look for porous, 'rusty' looking masses.