igneous and metamorphic derivative (weathered)
Limonitic Gossan
Goethite/Limonite aggregate after sulfide
Hardness 4-5.5 (variable); Yellow-brown to rusty red streak; Earthy to sub-metallic luster; Porous/vuggy texture; High iron content; Lacks distinct crystal systems due to amorphous nature.
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Physical properties
Hardness 4-5.5 (variable); Yellow-brown to rusty red streak; Earthy to sub-metallic luster; Porous/vuggy texture; High iron content; Lacks distinct crystal systems due to amorphous nature.
Formation & geological history
Formed through the intense oxidation and weathering of sulfide-rich ore bodies (like pyrite or chalcopyrite) near the Earth's surface. Groundwater dissolves sulfuric acid, leaving behind iron oxides and hydroxides.
Uses & applications
A critical geological indicator ('iron hat') used by miners to locate deeper base-metal and precious-metal deposits (gold, copper, silver). Historically used as low-grade iron ore.
Geological facts
Gossans are nicknamed 'iron hats' because they cap unweathered ore deposits. They were historically the first clue for prospectors in the 19th-century mining rushes.
Field identification & locations
Look for cellular 'boxwork' textures and intense rusty staining in rocky outcrops. Commonly found in mining districts like Arizona, Australia, or Cornwall.
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Other igneous and metamorphic derivative (weathered) specimens
Ambergris
Ambrein (C30H52O Derivative)
Organic (Zoogenic)
Asphalt Concrete
Bituminous conglomerate
sedimentary
Gossan (Iron Hat)
Limonitic Gossan (predominantly FeO(OH)·nH2O)
igneous/metamorphic derivative
Quartz (Milky/Common)
Silicon Dioxide (SiO2)
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Pyrite in Matrix (likely Quartz or Schist matrix)
Iron Sulfide (FeS2)
mineral
Corundum (Sapphire/Ruby in Matrix)
Aluminium oxide (Al2O3)
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