Jarosite KFe3(SO4)2(OH)6 Hexagonal
Description: Jarosite occurs as earthy pale yellow to brown coatings, crusts and granular masses formed by the alteration of pyrite, marcasite and other iron sulfides. It is likely much more common in the state than indicated, being likely at most localities listed for pyrite and marcasite. Its earthy, crumbly nature results in its being overlooked, cleaned off or discarded.
ROCK COUNTY: Jarosite is noted as an alteration product of pyrite associated with alunite, gypsum and lepidochrocite in the St. Peter Sandstone exposed in the silica sand quarry near Hanover. (Odom, Willard and Lassin, 1979).
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