Mineral

Yellow Ochre / Limonite

Limonite (FeO(OH)·nH2O)

Hardness: 4-5.5 (Mohs scale); Color: Yellowish-brown to deep orange; Luster: Dull or earthy; Crystal Structure: Amorphous (non-crystalline); Cleavage: None; Specific Gravity: 2.7-4.3

Hardness: 4-5
Color: Yellowish-brown to deep orange
Luster: Dull or earthy

Identified April 3, 2026More mineral →

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Physical properties

Hardness: 4-5.5 (Mohs scale); Color: Yellowish-brown to deep orange; Luster: Dull or earthy; Crystal Structure: Amorphous (non-crystalline); 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 mineral deposits like hematite, magnetite, or pyrite. It is common in soil and boggy environments.

Uses & applications

Historically used as a vital pigment (Yellow Ochre) for cave paintings and pottery. Industrially, it is used as a low-grade iron ore and as a coloring agent in concrete and paints.

Geological facts

Limonite is not a true mineral but a mixture of hydrated iron oxide minerals. It was one of the first pigments used by prehistoric humans in cave art around the world.

Field identification & locations

Identify by its earthy appearance and yellow-brown streak (produced by scratching it against unglazed porcelain). It is commonly found in sedimentary rock beds and gossans (iron caps over ore deposits).