sedimentary

Gossan (with Limonite and Hematite)

Gossanous iron-oxide rock (Fe2O3 · nH2O)

AI-generated identification · may be incorrect

Hardness: 4.0-5.5 (variable); Color: Ochre, rusty brown, dark reddish-purple; Luster: Dull to sub-metallic; Structure: Porous, cellular, or massive; Cleavage: None; Specific Gravity: 2.7-4.3.

Hardness: 4
Color: Ochre, rusty brown, dark reddish-purple
Luster: Dull to sub-metallic

Identified June 19, 2026More sedimentary →

Explore Gossan (with Limonite and Hematite) in the encyclopedia →

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 (variable); Color: Ochre, rusty brown, dark reddish-purple; Luster: Dull to sub-metallic; Structure: Porous, cellular, or massive; Cleavage: None; Specific Gravity: 2.7-4.3.

Formation & geological history

Formed by the intense oxidation and weathering of sulfide mineral deposits (like pyrite or chalcopyrite) in an oxygen-rich environment above the water table.

Uses & applications

Used historically as an indicator for underlying ore deposits (gold, silver, copper). Sometimes used as a source for iron pigments (ochre).

Geological facts

Miners call the reddish-brown cap 'the iron hat.' It acts as a geological signpost, often leading to rich metal deposits deeper underground.

Field identification & locations

Identify by its 'rusty' appearance and porous texture. Commonly found in mining districts and arid regions. Collectors should look for boxwork textures which indicate former crystals.