Silver Hill Mine, Silver Hill, Silver Hill Mining District, Carolina Slate Belt, Davidson County, North Carolina, USAi

Regional Level Types
Silver Hill Mine	Mine
Silver Hill	Hill
Silver Hill Mining District	Mining District
Carolina Slate Belt	Belt
Davidson County	County
North Carolina	State
USA	Country

A former Au-Ag-Pb-Zn-Cu occurrence/mine located , 8.9 miles SSE of Lexington and 7.0 miles NW of Denton, on private land. The first year of production was 1838 and the last was 1938, with activity during the periods 1838-1868, 1898-1900, and 1938. The USGS MRDS database stated accuracy for this locality is 10 meters.

This mine was originally worked in 1838 as King's Mine and was later known as the Washington Silver Mine. The deposit was actively mined from 1840 to 1855. Since 1882 work was intermittent. During early work, mining was carried out from a shaft 650 feet deep. The shaft was deepened to 750 feet during the period from 1898 to 1900.

Mineralization is a polymetallic deposit (Mineral occurrence model information: Model code: 184; USGS model code: 28a; Deposit model name: Massive sulfide, kuroko; Mark3 model number: 93), hosted in argillite of the Mudstone Member of the Cid Formation. The ore body is comprised of West-plunging lenses that dip 45-65NW at a thickness of 5 meters, a length of 61 meters and a depth-to-bottom of 213 meters. Two lenses (230 X 7 X 61 meters) and (65 X 5 X 91 meters) were exploited. Controls for ore emplacement included a favorable stratigraphic layer within The upper Cid Mudstone Member. Local alteration includes alteration to chlorite, calcite, tremolite, sericite, and epidote. Associated rocks include Early Cambrian andesite of the Cid Formation. Local rocks include rocks of the Cid Formation; meta-mudstone and meta-argillite.

The country rock is a thin-bedded argillite that is locally sheared to a gray to buff, quartz-sericite phyllite. Fractures in the rock are filled with quartz veinlets containing galena, pyrite and sphalerite. The dumps contain sericitized crystal tuff and a green-gray, saccharoidal quartz and feldspar rock with sparse, finely disseminated pyrite, malachite and hemimorphite. Most of the pyrite and chalcopyrite appears concentrated in the chlorite; while sphalerite is concentrated in fractures in quartz. In places calcite, tremolite and actinolite form a distinct rock type containing pyrite, chalcopyrite, galena, sphalerite and quartz stringers. The ore is primarily sphalerite and galena in a fine-grained mixture. Clear quartz and calcite are mixed with the ore in gash fractures. Hemimorphite coats some sphalerite. Brochantite, chrysocolla and goethite are found in some quartz stringers. Intermediate and felsic volcanic rocks are submarine pyroclastic rocks that may show grading and slump structures. These rocks are enclosed by rhythmically laminated mudstones. Size gradients and thickening of the volcanic section indicate the volcanic center may lie W (down-dip) of the deposit. Sulfide-rich rocks laterally grade into cherts that extend up to 200 meters on either side of the ore body. Tremolite may have formed from the metamorphism of dolomite beds or Ca-Mg alteration pipes associated with the massive sulfide. A Manganese-rich horizon consisting of rhodochrosite and calcite between the 60 and 100 foot levels, accompanies the base metal accumulations.

Regional geologic structures include the Gold Hill Fault Zone that produces cleavage of N15-30E with an 80NW dip. East of the deposit broad folds produce N50E, 50NW axial planar cleavage. local structures include bedding with a 45-65 degree, NW dip. Near the hinge of the anticline the limbs dip 80NW. 0.5 to 4 meter, vertically dipping shear zones are encountered underground. Two parallel, concordant ore beds are moderately plunging along bedding to the NW.

Workings include underground openings. Workings at the site have an overall depth of 228 meters, an overall length of 182.88 meters and an overall width of 7 meters. Two vertical shafts (North shaft & Sawmill shaft) connect with the third, inclined shaft at the 250 foot level and the 100 and 150 levels, respectively. The inclined shaft followed the long axis of the ore body at about 45 degrees. Drifts were completed at 50 foot intervals below the 100 foot level. The North shaft was completed to 216 feet and connected to the 200 foot level of the incline. The inclined shaft followed the E vein for about 725 feet. A vertical shaft connected with the inclined shaft. Two veins were worked by a series of crosscuts from these shafts.

Analytical data results: Assays from drilling average 40% Zn, 19% Pb, and 0.6% Cu. Mineralogically, 200 analyses of ore averaged 21.9% galena, 17.1% pyrite, 59.2% sphalerite and 1.8% chalcopyrite. Au was found from a trace to 25 ounces per ton and Ag from 4 to 120 ounces per ton values were reported (Pardee and Park).

Other Databases

Wikipedia:	https://en.wikipedia.org/wiki/Silver_Hill_Mine

Localities in this Region

Other Regions, Features and Areas containing this locality

References