sedimentary

Ironstone (Limonite/Hematite)

Ferruginous sedimentary rock (Fe2O3·nH2O / Fe2O3)

AI-generated identification · may be incorrect

Hardness: 4-5.5 on Mohs scale; Color: Rusty brown, reddish-orange, earthy yellow; Luster: Dull to earthy; Crystal Structure: Amorphous or microcrystalline; Cleavage: None; Specific Gravity: 3.3-4.3

Hardness: 4-5
Color: Rusty brown, reddish-orange, earthy yellow
Luster: Dull to earthy

Identified May 28, 2026More sedimentary →

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Physical properties

Hardness: 4-5.5 on Mohs scale; Color: Rusty brown, reddish-orange, earthy yellow; Luster: Dull to earthy; Crystal Structure: Amorphous or microcrystalline; Cleavage: None; Specific Gravity: 3.3-4.3

Formation & geological history

Formed by the chemical precipitation of iron minerals in marine or swampy environments, or by the oxidation of iron-rich minerals in soil. Often associated with the Phanerozoic eon.

Uses & applications

Historically used as iron ore. Today used primarily as an industrial pigment (ochre), in landscaping, and as a collector's specimen.

Geological facts

Ironstone is what gives many 'Red Rocks' parks their color. It often forms 'concretions' which can be mistaken for fossils or meteorites due to their weight and appearance.

Field identification & locations

Identify by its heavy weight (relative to other rocks), rusty streak, and lack of magnetism (unlike magnetite). Common in coal-bearing areas and desert regions.