mineral

Limonite and Hematite Gossan

Hydrated Iron Oxide Mix (FeO(OH)·nH2O) / Ferric oxide (Fe2O3)

Hardness: 4-5.5 (Mohs scale); Color: Rusty orange, reddish-brown, yellowish-ochre; Luster: Dull to earthy; Crystal structure: Amorphous to microcrystalline; Cleavage: None; Specific gravity: 2.7-4.3

Hardness: 4-5
Color: Rusty orange, reddish-brown, yellowish-ochre
Luster: Dull to earthy

Identified May 25, 2026More mineral →

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Physical properties

Hardness: 4-5.5 (Mohs scale); Color: Rusty orange, reddish-brown, yellowish-ochre; Luster: Dull to earthy; Crystal structure: Amorphous to microcrystalline; Cleavage: None; Specific gravity: 2.7-4.3

Formation & geological history

Formed by the intense chemical weathering and oxidation of iron-rich sulfide minerals (like pyrite) in the upper parts of an ore deposit, creating a 'rusty cap'.

Uses & applications

Historically used as iron ore and as a source of ochre pigments for paints; highly valued by prospectors as an indicator of deeper metal deposits (copper, gold, or silver).

Geological facts

Gossans were known to early miners as 'iron hats'. Because they are resistant to further weathering, they often outcrop prominently, leading miners directly to valuable veins beneath the surface.

Field identification & locations

Identify by its distinctive 'rusty' appearance and porous, boxwork texture. Heavy weight for its size suggests high iron content. Common in desert mining districts like Arizona or Western Australia.

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mineral