Jarosite

specimen number:
2354160

location:
Goldfield, Esmeralda Co., Nevada, USA

description:
Rich sparkling brown micro crystals of jarosite across the top of matrix. Good rich hand sized example for the species.

Located in Esmeralda County, Nevada, Goldfield is a legendary mining district that experienced a massive gold rush in the early twentieth century following major discoveries in 1902. The region's geology is characterized by Tertiary volcanic host rocks, including dacites and rhyolites, that underwent intense hydrothermal alteration during gold-bearing epithermal mineralization. Magmatic-hydrothermal activity introduced rich vein systems and led to widespread argillic and advanced argillic alteration, converting primary volcanic minerals into alunite, quartz, clays, and abundant iron sulfate minerals. Among these, jarosite formed extensively in the upper oxidized zones of the ore deposits as a prominent yellow-brown secondary sulfate, created by the breakdown of iron sulfides like pyrite under acidic, oxidizing conditions. Historical production yielded millions of ounces of gold from underground mines during the peak town boom between 1904 and 1910, and the abundance of jarosite and associated alteration minerals served as vital visual prospecting indicators for miners and mineral collectors exploring the district's extensive oxidized ore bodies.

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