sedimentary
Gossan (Iron Hat)
Goethite-Hematite rich weathered rock (Fe-hydroxides)
Hardness: 5-5.5 (variable), Color: Rusty brown, reddish-orange, earthy yellow, Luster: Dull to sub-metallic, Texture: Porous, vuggy, or boxwork, Specific Gravity: 3.3-4.3
- Hardness
- 5-5
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Physical properties
Hardness: 5-5.5 (variable), Color: Rusty brown, reddish-orange, earthy yellow, Luster: Dull to sub-metallic, Texture: Porous, vuggy, or boxwork, Specific Gravity: 3.3-4.3
Formation & geological history
Formed by the oxidation and leaching of sulfide mineral deposits at or near the surface. The coordinates in Papua New Guinea (Western Highlands) are consistent with the weathering of copper-gold porphyry systems common in the New Guinea Orogenic Belt.
Uses & applications
Historically used as an indicator for underlying ore deposits (gold, silver, copper). Sometimes used as low-grade iron ore or natural pigment.
Geological facts
Gossans are known as 'iron hats' because they sit atop unweathered ore bodies. Miners in the 19th century looked for this specific rusty texture to discover hidden mineral riches beneath the surface.
Field identification & locations
Identify by its distinct rusty 'burnt' appearance, heavy weight compared to surrounding soil, and honeycomb (boxwork) texture. Found in mineralized volcanic/metamorphic belts.
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