mineral

Limonite (often after Pyrite)

Limonite (FeO(OH)·nH2O)

AI-generated identification · may be incorrect

Hardness: 4-5.5; Color: Yellowish-brown to dark brown; Luster: Dull/Earthy to sub-metallic; Crystal structure: Amorphous; Streak: Yellow-brown; Specific Gravity: 2.7-4.3

Hardness: 4-5
Color: Yellowish-brown to dark brown
Luster: Dull/Earthy to sub-metallic

Identified June 26, 2026More mineral →

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Physical properties

Hardness: 4-5.5; Color: Yellowish-brown to dark brown; Luster: Dull/Earthy to sub-metallic; Crystal structure: Amorphous; Streak: Yellow-brown; Specific Gravity: 2.7-4.3

Formation & geological history

Secondary mineral formed from the chemical weathering of iron-rich minerals such as pyrite, magnetite, and siderite. Often found in oxidized zones of ore deposits and as bog iron.

Uses & applications

Historically used as an iron ore; currently used as a pigment (ochre) for paints and dyes. Small specimens are collected for geological study.

Geological facts

Limonite is not a true mineral but a mixture of hydrated iron oxides. It is responsible for the yellowish-brown coloring in many soils and weathered rock surfaces.

Field identification & locations

Identify by its characteristic yellow-brown streak and earthy appearance. Commonly found in sedimentary ironstones and as 'gossans' over mineral veins. Check for pseudomorphs after cubic pyrite.