mineral

Yellow Ocher (Limonite)

Limonite (Hydrated Iron Oxide) - FeO(OH)·nH2O

AI-generated identification · may be incorrect

Hardness: 4.0–5.5 on Mohs scale; Color: Yellowish-brown to deep yellow; Luster: Dull, earthy; Crystal Structure: Amorphous (often pseudomorphic after other iron minerals); Specific Gravity: 2.7–4.3

Hardness: 4
Color: Yellowish-brown to deep yellow
Luster: Dull, earthy

Identified March 11, 2026More mineral →

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Physical properties

Formation & geological history

Formed as a secondary material through the oxidation and weathering of primary iron-bearing minerals (like pyrite, magnetite, or siderite). It is often found in the oxidation zones of ore deposits or as a bog iron precipitate in swampy areas.

Uses & applications

Historically and currently used as a natural pigment (ocher) for paints, dyes, and cosmetics. It is also an accidental iron ore and used in geological education as a primary example of chemical weathering.

Geological facts

Limonite was one of the first pigments used by early humans in cave paintings (such as at Lascaux, France). Because it lacks a crystalline structure and contains variable amounts of water, it is technically a 'mineraloid' rather than a true mineral.

Field identification & locations

Identify in the field by its distinct mustard-yellow earthy streak when rubbed against a tile, its dusty texture, and its common occurrence near rusting iron-rich rocks. It is found globally in sedimentary and weathering environments.