Gossan

An iron and manganese-bearing weathered product overlying a sulphide deposit. It is formed by the oxidation and leaching-out of sulphides and carbonates, with the loss of the sulphur and most metals, leaving hydrated iron oxides (limonite, hematite etc.) and manganese oxides, quartz and relatively insoluble minerals. Also spelled gozzan. Synonymous with capping, iron hat, Eiserner Hut (German, from which the English name was derived) and chapeau de fer (French). See also oxidized zone, false gossan.