sedimentary

Yellow Ochre (Limonite)

Limonite (FeO(OH)wH2O)

Hardness: 4-5.5 (Mohs scale), Color: Yellow to brownish-yellow, Luster: Dull or earthy, Crystal Structure: Amorphous/microcrystalline, Cleavage: None, Specific Gravity: 2.7-4.3.

Hardness: 4-5

Identified July 12, 2026More sedimentary →

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Physical properties

Hardness: 4-5.5 (Mohs scale), Color: Yellow to brownish-yellow, Luster: Dull or earthy, Crystal Structure: Amorphous/microcrystalline, Cleavage: None, Specific Gravity: 2.7-4.3.

Formation & geological history

Forms through the chemical weathering of iron-rich minerals such as pyrite, magnetite, and hematite in oxidizing conditions. It is often found in the oxidation zones over iron ore deposits.

Uses & applications

Historically used as a natural pigment in art and paints. It is also a minor ore of iron and sometimes used as a flux in glassmaking.

Geological facts

Yellow ochre is one of the oldest pigments used by humans, found in prehistoric cave paintings dating back tens of thousands of years. It was highly valued in ancient Egypt and Rome.

Field identification & locations

Identify by its distinctive mustard-yellow color and yellow-brown streak. It often leaves a powdery residue when handled. Found worldwide in clay-rich soils and bog iron deposits.