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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.



(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. Gossans consist primarily of iron oxides and hydrous iron oxides (goethite, hydrogoethite, hydrohematite, turgite), and as a result they are usually dark or light red, ocherous, or brownish red in color. The formation of gossans is associated with the oxidizing action of surface waters and is accompanied by the secondary enrichment of ore deposits. In the process of weathering, the sulfides of copper, silver, zinc, and other metals oxidize to easily soluble sulfates, after which they are leached and carried to deeper parts of the ore body. At the same time the iron in sulfurous compounds—pyrite, chalcopyrite, and other sulfides—is only partially removed in the form of a soluble salt (sulfate of iron oxide); most of the iron is oxidized and hydrated and remains in place in the form of hydrates of iron oxide (brown iron ores). These secondary brown iron ores, occurring as a result of the transformation of original pyritic and other ores containing iron sulfides, are what form the gossans near the earth’s surface. The depth at which gossans are found beneath the earth’s surface is usually restricted to the groundwater level and may extend to dozens or even hundreds of meters. In comparison with initial sulfide ores gossans are richer in iron in their upper parts and in gold in their lower parts. Contrasting strongly with the enclosing rocks, gossans serve as an important indicator in explorations for sulfide-ore deposits and in identifying the primary ores concealed in the depths.


Smirnov, S. S. Zona okisleniia sul’fidnykh mestorozhdenii, 3rd ed. Moscow-Leningrad, 1955.
Saukov, A. A. Geokhimiia, 3rd ed. Moscow, 1966.


References in periodicals archive ?
Exploration Review: Rock and soil geochemical results collected by Gentor at Karaburun have defined widespread Cu-Zn-Ag-Au and Co anomalism coincident with numerous stacked stratigraphic mineralised gossan horizons - numbered Main and 1 to 8.
Kris Butera has stood down as director and CEO of Gossan Hill and will continue as a Senior Consultant to Gossan Hill.
We are concentrating on de-risking the Seymourville frac sand project," said Charles Gryba, president of Claim Post Resources, "We want to independently compile all of the Gossan and government drilling into a single database prior to starting our own sonic drill program to confirm and expand the size of the resource.
We continue to grieve with the families even as we close this grim chapter of the Big Gossan incident," said Rozik B.
The gold and silver mineralization at the Gossan Hill project is located along a 2 kilometer shear zone.
Results have confirmed the characteristics of the gossan system to be compatible with their initial classification as nickel-copper bearing magmatic massive sulphide gossans.
RenGold's technical staff recognized the Big Gossan copper project by proprietary satellite alteration mapping, which identified a gossan on the margin of a skarn-bearing Cretaceous granodiorite at the south end of the Sahwave Mountains in southern Pershing County, Nevada.
On 17 July 2013 Gossan Hill entered into a Farm in and JV agreement with PMR with respect to the Peel Fault Gold project located near Tamworth.
90 meter intersection was received from hole GOS43, which was collared 650 meters south of the previous drilling associated with the Gossan Hill zone, and appears to be on the same horizon / structure as the mineralized intersections recovered from the 2011 program.
Sydney, Australia, Oct 28, 2013 - (ABN Newswire) - Sovereign Gold Company Limited (ASX:SOC), through subsidiary Gossan Hill Gold Limited, is pleased to announce the discovery of high grade gold mineralisation outside of the Hobbs 1 Pipe, providing further encouragement that the Mt Adrah district will potentially host gold mineralisation additional to the current resource.
V: CNX)(OTCQX: CLLXF) has received results from a metallurgical test program conducted on drill core samples from their Gossan Hill property.
Drilling activity began on 28 July by collaring the first hole, KW06-01, within a gold-in-soil anomaly on the Gossan Ridge prospect identified during the 2005 field program.