Gossan (eiserner hut or eisenhut) is intensely oxidized, weathered or decomposed rock, usually the upper and exposed part of an ore deposit or mineral vein.
Definition of GOSSAN. : decomposed rock or vein material of reddish or rusty color that results from oxidized pyrites. ADVERTISEMENT Gossan. (iron hat), a residual formation that occurs in the surface parts of ore (primary sulfide) deposits of copper, lead, zinc, and other metals as a result of chemical weathering and oxidation of the primary minerals of the ore body. (geology). A rusty, ferruginous deposit filling the upper regions of mineral veins and overlying a sulfide deposit; formed by oxidation of pyrites. Also known as capping; gozzan; iron hat. Frequently gossan appears as a red stain against the background rock and soil due to the abundance of oxidized iron and the gossan may be a topographic positive area due to the abundance of erosion resistant quartz and iron oxides. In the 19th and 20th centuries gossans were important guides to buried ore deposits used by prospectors in their quest for metal ores. An experienced prospector could read the clues in the structure of the gossans to determine the type of mineralization likely to be found below the iron cap. Back to gossan. Pyrite is just iron sulfide. When it weathers, it produces a chemical reaction that releases heat yielding sulfuric acid (H2SO4), rotten egg gas (Fe2S) and rust (Fe203, Fe0H). If you have ever been close to any politician, you have a good idea of what hydrogen-sulfide (rotten egg gas) smells like. Gold in the San Juan Mountains of Colorado. As a gold prospector you should immediately notice the mine dumps, lack of trees growing on the yellow, brown, reddish brown and tawny colored rock and soil known as gossan. gos·san. n. An exposed, oxidized portion of a mineral vein, especially a rust-colored outcrop of iron ore. [Cornish.  1. n. Decomposed rock, usually reddish or ferruginous (owing to oxidized pyrites), forming the upper part of a metallic vein. Character of the gossan Ores.—The residual gossan ores are commonly spongy or cellular in character, but this characteristic is not unfailing, .... 4. Mineral Resources of Virginia by Thomas Leonard Watson, Ray Smith Bassler, Heinrich Ries, Roy Jay Holden (1907). The name gossan appears to come from Cornish miner's slang. It comes from the Cornish gossen, from gōs meaning blood, from Old Cornish guit. The terms iron cap and iron hat, common in America, are direct translations from the German  eisenhut , which term was also used in America. In the 19th and 20th centuries gossans were important guides to buried ore deposits used by prospectors in their quest for metal ores. An experienced prospector could read the clues in the structure of the gossans to determine the type of mineralization likely to be found below the iron cap. Gossan (eiserner hut or eisenhut) is intensely oxidized, weathered or decomposed rock, usually the upper and exposed part of an ore deposit or mineral vein. In the 19th and 20th centuries gossans were important guides to buried ore deposits used by prospectors in their quest for metal ores. An experienced prospector could read the clues in the structure of the gossans to determine the type of mineralization likely to be found below the iron cap. A large sulfide deposit, as it ages at the surface, may gradually gain a thick cap of iron oxide mineralsa gossan. Gossan may also mean the red oxide material itself. The word gossan comes from the Cornish language and refers to the red color of the oxidized iron minerals. It may also be called an iron hat or the French chapeau de fer or the German eisenhut. Gossans are primarily iron oxides such as hematite and goethite, or the intimate mixture of both called limonite.  gossan. (geology). A rusty, ferruginous deposit filling the upper regions of mineral veins and overlying a sulfide deposit; formed by oxidation of pyrites. Also known as capping; gozzan; iron hat.
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what is a gossan