Mineral

Limonite (also known as Yellow Ochre or Brown Hematite)

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

Hardness: 4-5.5 on Mohs scale; Color: Yellowish-brown to dark brown; Luster: Dull, earthy, or sub-metallic; Crystal Structure: Amorphous (does not form distinct crystals); Specific Gravity: 2.7–4.3; Cleavage: None.

Hardness: 4-5
Color: Yellowish-brown to dark brown
Luster: Dull, earthy, or sub-metallic

Identified March 23, 2026More mineral →

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Physical properties

Formation & geological history

Formed as a secondary mineral through the weathering of iron-rich ores such as magnetite, pyrite, and hematite. It often forms in swampy or boggy environments (bog iron ore) and is found in sedimentary deposits across various geological ages from the Precambrian to recent.

Uses & applications

Historically used as a primary iron ore and as a pigment for ochre paint. Current uses include industrial coloring for dyes, masonry, and as a low-grade iron source. It is also collected by mineralogists for its variety of forms like stalactites or pseudomorphs.

Geological facts

Limonite is not a true mineral in the strictest sense but a mixture of related hydrated iron oxide minerals, mostly goethite. It was one of the earliest pigments used by humans, found in Neolithic cave paintings.

Field identification & locations

Identify in the field by its distinct yellowish-brown 'streak' (the color it leaves when rubbed on unglazed porcelain) and its earthy smell when damp. It is commonly found in iron-rich soils, weathered mineral veins, and at the bottoms of bogs.

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