Golden Center Mine (Garage vein; Sleep vein; Church Hill vein), Golden Center group (Cabin Flat Mine; Rock Roche Mine; Dromedary Mine; Scotia Mine; Peabody Mine; Garage/Dromedary/Berriman/Peabody), Grass Valley, Grass Valley Mining District, Nevada County, California, USAi

Regional Level Types
Golden Center Mine (Garage vein; Sleep vein; Church Hill vein)	Mine
Golden Center group (Cabin Flat Mine; Rock Roche Mine; Dromedary Mine; Scotia Mine; Peabody Mine; Garage/Dromedary/Berriman/Peabody)	- not defined -
Grass Valley	Valley
Grass Valley Mining District	Mining District
Nevada County	County
California	State
USA	Country

A former lode Au-Ag occurrence/mine located in sec. 27, T16N, R8E, MDM, 0.5 km (0.3 mile) SW of Grass Valley (coordinates of record), on private land. Discovered before 1850. MRDS database stated accuracy for this location is 100-500 meters. The Golden Center Mine is a consolidation of the Rock Roche, Dromedary, and Berriman Mines. Location selected by the USGS for latitude and longitude represents the Golden Center Mine main shaft symbol on the 1949 version of the USGS Grass Valley 7.5-minute quadrangle. On later versions of the map the symbol has been replaced by State Highway 49 improvements.

The Golden Center Mine, located within the town limits of Grass Valley, is a consolidation of the previous Rock Roche, Dromedary, and Berriman Mine properties along with other mineral rights under the town of Grass Valley totaling 150 acres. The mine was first worked in the early 1850s, again in 1863, and from 1868 to 1874, when the ore is reported to have ranged from between $10 and $60/ton.

In 1912, the mine was acquired by the Grass Valley Mining Company, which sunk the present (Johnston, 1940) shaft to the 1,100-foot level and crosscut on the 500-level to the Garage, Sleep, and Church Hill veins. In 1931, the mine was acquired by Cooley Butler of Los Angeles. Between 1931 and 1934, the shaft was deepened to the 1,300-foot level, and the 1,100-foot crosscut to the Garage and Church Hill veins was driven. Total value of the mine's production between the 400- and 1,300-level has been estimated at $2,250,000 (period values) (Johnston, 1940).

Mineralization is a vein deposit (Mineral occurrence model information: Model code: 273; USGS model code: 36a: Deposit model name:Low-sulfide Au-quartz vein; Mark3 model number: 27), hosted in Early Cretaceous granodiorite. The ore body is tabular. Controls for ore emplacement involved mineralization that occurs as erratic shoots within mesothermal gold-bearing quartz deposited within fracture zones. Local alteration included ankeritic, sericitic, and pyritic replacement of wall rocks adjacent to veins. Local rocks include Mesozoic granitic rocks, unit 3 (Sierra Nevada, Death Valley area, Northern Mojave Desert and Transverse Ranges).

The principal veins in the Golden Center Mine are the Dromedary, Garage, Church Hill, and Sleep. All strike north and northeast and dip west or northwest and all are contained wholly within granodiorite (Johnston, 1940).

Most of the quartz in the various veins is massive and milky. Combs and sheared and brecciated textures are common. Locally, chalcedony fills the interstices in combs and cements quartz breccias. Pyrite, galena, and chalcopyrite are the principal sulfides.

Dromedary Vein: The Dromedary vein is the main producing zone in the mine. It has an average strike of N 35? E and an average dip of 38? NW. In the main shaft, the strike of the vein is approximately N-S, but N of the shaft, the strike swings to the NE where the vein is intersected by a series of strong crossing fractures. The angular divergence in strike between the vein and the crossings ranges between 0 and 30 degrees. The vein is repeatedly offset on the crossings, which dip 70 to 90 degrees, forming a series of steps (Johnston, 1940, figure 47).

The Dromedary vein was readily followed in the shaft to the 1,100-level and stoping established the continuity of the vein on the north side of the shaft. Below the 1,100-foot level the shaft cut a strong crossing, along which much water circulated and upon which the vein abruptly steepened. Beyond the crossing at the 1,300-foot station the vein was not found.

Garage vein: The Garage vein, which strikes northeast and dips 38? NW, roughly paralleling the Dromedary vein and lying in its hanging wall, was first encountered on the 500-foot level crosscut. The Garage vein is less broken than the Dromedary vein. The quartz ranges from 2 or 3 to 20 inches thick. Usually it is frozen to one wall; commonly to both walls. In places it fills a splintered fracture several feet wide, forming a sheeted zone of narrow quartz seams.

Church Hill vein: Like the Garage vein, which it parallels, the Church Hill vein was first found on the 500-foot crosscut near its junction with a footwall split called the Sleep vein. A short distance east of the discovery point, an ore shoot was encountered. A winze was sunk at the junction of the Church Hill and Sleep veins and a sub-level driven through the ore. On the sub-level, the shoot was about 135 feet long and averaged 14 inches of quartz that contained a little over 2 ounces of Au per ton. Structurally, the Church Hill vein more closely resembles the Garage vein than the Dromedary vein, for the vein walls are close together and the quartz is commonly frozen to them. Ribbon structure and quartz breccias are also present on the 500- and 1,100-foot levels.

Regional geologic structures include the Wolf Creek Fault Zone, Gillis Hill Fault and the Melones Fault Zone.

Workings include underground openings. A map of the underground workings in the Golden Center Mine is included in Johnston (1940, Plate 25, page 74).

Ore materials include free-milling fine to coarse gold in quartz plus auriferous pyrite and galena. Gangue materials include quartz, calcite, chalcedony, chalcopyrite, sphalerite.

Total production from the Golden Center Mine is estimated at $2,250,000 (Johnson, 1940).

Other Databases

Link to USGS MRDS:	10261546

Other Regions, Features and Areas containing this locality

References