Nenzel Hill, Rochester Mining District, Pershing County, Nevada, USAi

Regional Level Types
Nenzel Hill	Hill
Rochester Mining District	Mining District
Pershing County	County
Nevada	State
USA	Country

The Rochester District, in Pershing County, Nevada, was prospected beginning just after the Civil War. Early discoveries were of vein and placer gold. In the heart of the Rochester District is a topographic high called Nenzel Hill, named for Joseph Nenzel whose wife inherited a group of claims staked by her uncle around 1905. Nenzel discovered quartz veins containing very fine grained, dispersed argentite there around 1912. The discovery came very late in the history of gold and silver in the American west perhaps because of the very nondescript nature of the ore. The discovery of other similar vein silver deposits followed but those on Nenzel Hill were the most productive.

The Rochester District is underlain by late Paleozoic and Triassic age volcanics. Common among these volcanics are rhyolites have frequently been altered to a quartz-sericite-pyrite mineral assemblage. Deformation and the intrusion of granite porphyry and other granitic lithologies occurred in the Cretaceous. It is most likely that the silver-gold mineralization developed during this later phase of volcanism.

Most of the productive ore deposits, worked in the initial pulse of activity in the district, are vein-type occurrences. However, in large areas the country rock is cut by networks of small mineralized fractures, the whole of which is known as stockworks. In the initial period of mining the stockworks were not economically viable except at the Nevada Packard mine south of Nenzel Hill.

Today, in a much different economic and technological environment the stockworks have gained supreme importance. Vikre (1981) noted that the low grade silver-gold ore in the area around Nenzel Hill amount to 100 million tons. Since the mid-1980's that area, including Nenzel Hill, has become part of a large open pit mine operated by Coeur Rochester. A subsidiary pit has been developed south of the Nenzel Hill area on the site of the former Nevada Packard Mine.

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