mineral

Limonite (Iron Stone/Ocher)

Limonite (FeO(OH)·nH2O)

Hardness: 4.0-5.5 (Mohs scale), Color: Yellowish-brown to dark brown/black, Luster: Dull to earthy, Crystal Structure: Amorphous/Microcrystalline, Specific Gravity: 2.7-4.3

Hardness: 4

Identified April 8, 2026More mineral →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness: 4.0-5.5 (Mohs scale), Color: Yellowish-brown to dark brown/black, Luster: Dull to earthy, Crystal Structure: Amorphous/Microcrystalline, Specific Gravity: 2.7-4.3

Formation & geological history

Formed by the oxidation (weathering) of iron-rich mineral deposits such as pyrite, magnetite, and hematite in sedimentary or hydrothermal environments.

Uses & applications

Historically used as a yellow and brown pigment (ocher) for cave paintings and pottery. Minor source of iron ore and a common collector specimen for educational purposes.

Geological facts

Limonite is not a 'true' mineral but a mineraloid mixture of hydrated iron oxides. It was the primary source of color for ancient human artwork dating back tens of thousands of years.

Field identification & locations

Identify in the field by its distinct mustard-yellow to rust-brown streak (powder color), earthy texture, and association with wet, oxidizing environments. Commonly found in marshy areas as 'bog iron'.