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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 ?
Over the past 18 months we have been systematically narrowing in on a potential copper-gold porphyry discovery at the Thursday's Gossan prospect and we are now well funded into the next phase of exploration drilling at this very exciting prospect.
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.
V - CNX), a company that explores and develops mineral properties in Canada, has reported that a drilling permit has been received for their Gossan Hill Property, near Cranberry Portage, Manitoba.
Results have confirmed the characteristics of the gossan system to be compatible with their initial classification as nickel-copper bearing magmatic massive sulphide gossans.
The gold-enriched gossan, based on results of six intersections, averages 4.
Stavely Minerals' Managing Director, Mr Chris Cairns, said the confirmation of a compelling drilling target at Toora West followed hard on the heels of its recently announced exploration breakthrough at Thursday's Gossan.
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.
Gossan Resources Limited has bought a new property in the zinc-rich polymetallic Sturgeon Lake Greenstone Belt in northwestern Ontario comprising 15 claims that total 3,344 hectares.