mineral

Gossan (Iron Hat)

Hydrous Iron Oxides (predominantly Goethite FeO(OH) and Limonite)

AI-generated identification · may be incorrect

Hardness: 5.0-5.5 (variable); Color: Rust-red, yellow, brown; Luster: Dull or earthy; Crystal Structure: Amorphous/Orthorhombic; Cleavage: None; Specific Gravity: 3.3-4.3

Hardness: 5
Color: Rust-red, yellow, brown
Luster: Dull or earthy

Identified June 29, 2026More mineral →

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Physical properties

Hardness: 5.0-5.5 (variable); Color: Rust-red, yellow, brown; Luster: Dull or earthy; Crystal Structure: Amorphous/Orthorhombic; Cleavage: None; Specific Gravity: 3.3-4.3

Formation & geological history

Formed by the oxidation and leaching of sulfide mineral deposits (like pyrite or chalcopyrite) at or near the Earth's surface. This process results in the removal of sulfur and metals, leaving behind a residue of iron oxides.

Uses & applications

Historically used as an indicator for underlying ore deposits such as copper, gold, or silver. Small amounts are used as mineral pigments (ochre).

Geological facts

Gossans were famously known as 'iron hats' by early miners because finding one often meant a rich vein of valuable metals lay just beneath the oxidized surface.

Field identification & locations

Identified by its porous (vuggy) texture and distinct rusty-orange to dark brown staining. Found in mining districts globally where sulfide veins outcrop.