Keystone Mine, Willard Mining District, Pershing County, Nevada, USAi

Regional Level Types
Keystone Mine	Mine
Willard Mining District	Mining District
Pershing County	County
Nevada	State
USA	Country

Keystone Mine, Willard Mining District,Mill City Mining District, Nevada, USA

Sec 1-12 T34N R34E. Silver-lead-copper mine.
Note: Coordinates deleted because obviously wrong.

Deposit type: Low-sulfide Au-quartz vein



Structure:Gently Dipping Shear Zones

Alteration:
Sericitization, Silicification, Kaolinization, Pyritization

Commodity:Scheelite was found in drill core of granodiorite for 22 ft along the core from a depth of 135 ft down.


Deposit: Ore zone varies from 2 to 6 ft in width. The mines are in granodiorite that cuts shale of Triassic age. Western (new) shaft sunk on n-s trending white quartz vein in shale; wallrock is moderately silicified, laced wit-h quartz-sulfide veinlets. At the old shaft to the NE, a N30E,-40 SE quartz vein occupies a shear zone in kaolinized granodiorite. Vein is 1-2 ft wide, iron and manganese oxide-stained. Vein contains galena, sphalerite, tetrahedrite in white quartz gangue. Parallel quartz veins cut both granodiorite and shale; granodiorite is generally kaolinized and laced with quartz veinlets. Some quartz on the dump displays pale green staining. S-hear zone is 200-300 ft wide and both old and new shafts are within it. Vein system seems to be stronger where it cuts granodiorite. To the NE at sample site 2656, old pits, shafts, cuts expose a series of N60-70 W NE-dipping quartz veins which cut hornfels and shale. The veins are 4-15 ft thick, are brecciated, and are iron-oxide stained on outcrop. Vein material on some of the dumps contains pods of massive pyrite. The hornfels wallrocks are bleached, kaolinized and contain disseminated pyrite. Vein material contains sphalerite, galena, some tetrahedrite and stibnite; model name could also be: polymetallic veins. Located in 1872, no development until 1937 when acquired by Nevada Keystone Co. Mine workings are in an area of shales and limestones which have been intruded by granodiorite dike. The Keystone mines are located in the granodiorite which cuts the shales of Triassic age. The Keystone mines were worked intermittently to 1966. info.src : 1 pub lit; 2 unpub rept; 3 field observ



The Keystone mines must have been worked in the 1870-1880's, evidence of old buildings can be seen in the wash east of the old shaft. Remains of an old horse whim can be seen at the northeastern workings.

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Link to USGS MRDS:	10042501

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References