mineral
Gossan / Iron Ore Rock
Hematite / Goethite / Limonite iron oxide assemblage
Hardness varies from 4 to 6.5 on the Mohs scale depending on specific iron minerals present; Color ranges from dark brown, reddish-brown, to yellowish-brown with extensive rust staining; Luster is earthy to sub-metallic; Crystal structure is amorphous to microcrystalline;…
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Physical properties
Hardness varies from 4 to 6.5 on the Mohs scale depending on specific iron minerals present; Color ranges from dark brown, reddish-brown, to yellowish-brown with extensive rust staining; Luster is earthy to sub-metallic; Crystal structure is amorphous to microcrystalline; High specific gravity (heavy for its size due to high iron content).
Formation & geological history
Formed through the surface weathering and oxidation of sulfide ore deposits (gossan cap), typically found in hydrothermal or magmatic-hydrothermal environments over geological time scales.
Uses & applications
Primary ore for iron extraction, used in the production of steel and metals; occasionally collected by mineral enthusiasts as an ore sample.
Geological facts
Gossans act as significant pathfinder or indicator formations for prospectors searching for hidden subsurface copper, gold, or polymetallic sulfide deposits.
Field identification & locations
Identify in the field by its distinct heavy weight, prominent rust-colored and brown weathering crust (iron oxides), and porous or spongy texture. Commonly found capping sulfide ore bodies worldwide.
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