Gold Hill Quartz Mine (Gold Hill Mine; Gold Hill Qtz), Empire Star group (Empire Star Mines Company holdings), Grass Valley, Grass Valley Mining District, Nevada County, California, USAi

Regional Level Types
Gold Hill Quartz Mine (Gold Hill Mine; Gold Hill Qtz)	Mine
Empire Star group (Empire Star Mines Company holdings)	- 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 secs. 27 & 34, T16N, R8E, MDM, about 1.6 km SW of Grass Valley proper, on Whale Hill (within the SW portion of the town of Grass Valley and W of Wolf Creek), on private (patented) land. Discovered in 1850. The property comprises 14.71 acres. MRDS database stated accuracy for this location is 100 meters. This is the site of gold discovery in Grass Valley. The location point selected for latitude and longitude by USGS represents the Gold Hill Mine symbol on Lindgren's 1896 1:14,400-scale Grass Valley Special Map (contained in Lindgren's 1896 Nevada City Special Folio) and transcribed onto the USGS Grass Valley 7.5-minute quadrangle.

Gold was first discovered in the Grass Valley District in quartz veins of Gold Hill on the outskirts of Grass Valley (within present-day Grass Valley) in 1850. These veins were the principal producers in the early days of the district. Almost immediately, the towns of Grass Valley and Nevada City were founded and went on to become permanent communities. Quartz mining was well established by 1857 and continued without interruption until the 1940's. The discovery at Gold Hill was followed by discoveries of veins at nearby Ophir Hill, Rich Hill, and Massachusetts Hill. And by 1867 most of the major mines of the district had been located.

The Gold Hill Mine operated from 1850 to 1867 and is reported to have produced $4,000,000 (period values) during this period. In 1903, the mine was purchased by the North Star Co., operators of the nearby North Star Mine. The North Star Co. did considerable development work in search of new ore bodies. No new ore was found, and the mine has remained idle ever since.

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 Mesozoic-Paleozoic diabase and Early Cretaceous granodiorite. The ore body is tabular, strikes N and dips 28E at a thickness of 1.83 meters. The vein is from a seam to 6 feet thick and averages 2 feet in thickness. The hanging wall is impregnated with pyrite. Controls for ore emplacement involve mineralization that occurs as erratic shoots within mesothermal gold-bearing quartz deposited within fracture zones. Local alteration include 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 Gold Hill and neighboring Massachusetts Hill (also called Rocky Bar) veins were among the earliest worked in the district. The veins strike generally to the north and dip 20° to 40° E or W. The veins lie either in granodiorite, porphyrite, or diabase.

The Gold Hill vein crops out in diabase, but all of the lower workings are in granodiorite. The strike of the vein though irregular, is generally north-south and the dip is 28? E. The upper portion, near the outcrop, is much flatter. The quartz vein is generally narrow varying from a mere seam to as much as 6 feet and averages 2 feet. At 275 feet south of the shaft, the vein is said to have been cut off by a fault striking northwest and containing no ore. The hanging wall of the vein is strongly impregnated with pyrite. The vein is characterized by irregular pay shoots, at places being almost entirely barren, while at other places large pockets of coarse gold occur. North of the Gold Hill shaft, the vein splits, one branch extending north and the other northeast (Johnston, 1940).

Gold occurred mainly as free gold, often as extremely rich masses of coarse mineralization. Both the Gold Hill and Massachusetts Hill veins were known for their heavy masses of gold (much more than the generally disseminated fine to coarse gold of the other veins). Gold in both veins averaged 850 fineness. Sulfides are generally poor grade.

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

include underground openings. Whale Hill is honeycombed with drifts and shafts. No information is generally available regarding the underground workings in the Gold Hill Mine. Information may be available in the archives of the Empire Mine State Park since the Gold Hill Mine was acquired by and worked by the North Star Mining Co. prior to its acquisition by the Empire Mine.

Ore materials include free-milling coarse and fine gold in quartz (850 fine), plus auriferous pyrite and galena. Gangue materials include quartz, calcite, chalcopyrite, and sphalerite.

Production data are found in: JOHNSTON, 1940

The Gold Hill Mine has reportedly produced $4,000,000 (period values) in gold.

Other Databases

Link to USGS MRDS:	10101258

Other Regions, Features and Areas containing this locality

References