Massachusetts Hill Quartz Mine (Massachusetts Hill Qtz; Rocky Bar Mine; Boston Ravine claim; Great Britain claim; New Rocky Bar claim; New York Hill claim; Polkinghorn claim; Rocky Bar claim; Stockbridge claim), Empire Star group (Empire Star Mines Company holdings), Grass Valley, Grass Valley Mining District, Nevada County, California, USAi

Regional Level Types
Massachusetts Hill Quartz Mine (Massachusetts Hill Qtz; Rocky Bar Mine; Boston Ravine claim; Great Britain claim; New Rocky Bar claim; New York Hill claim; Polkinghorn claim; Rocky Bar claim; Stockbridge claim)	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. 33 & 34, T16N, R8E, MDM, about 1.6 km (1 mile) SSW of Grass Valley proper. Mine is within the southern part of the town of Grass Valley on the west side of Wolf Creek, on private (patented) land. Discovered in 1850. The property comprises 54.69 acres. MRDS database stated accuracy for this location is . The location point selected by the USGS for latitude and longitude represents the Massachusetts Hill Mine dumps 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.

1850, gold was first discovered in the Grass Valley Mining District in quartz veins of Gold Hill immediately north of the Massachusetts Hill Mine within present-day Grass Valley. 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 1940s. The discovery at Gold Hill was followed by discoveries of veins at nearby Ophir Hill, Rich Hill, and Massachusetts Hill. By 1867, most of the major mines of the district had been located.

The Massachusetts Hill vein was worked from 1850 to 1866 with few interruptions. During this period about $3,000,000 (period values) is said to have been produced. The Massachusetts Hill Mine was worked through the old Rocky Bar deep shaft. The mine was acquired by the North Star Mining Co. in 1894 and between 1894 and 1901 produced $1,078,075 (period values) from 68,222 tons of ore, an average of $15.80 (period values) a ton. In 1901 the mine was closed.

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 granodiorite and diabase. The ore body is tabular in form. Controls for ore emplacement included mineralization that occurs as erratic shoots within mesothermal gold-bearing quartz deposited within fracture zones. Local alteration
includes ankeritic, sericitic, and pyritic replacement of wall rocks adjacent to veins. Local rocks include Mesozoic volcanic rocks, unit 2 (Western Sierra Foothills and Western Klamath Mountains) and/or 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. They are in general characterized by small width, but the ore was rich and gold was commonly coarse. Veins strike generally to the north and dip 20 to 40E or W. The veins lie either in granodiorite, porphyrite, or diabase.

Both veins were known for heavy masses of gold extracted from their veins (much more than the generally disseminated fine to coarse gold of the other veins). Gold produced from the Massachusetts Hill Mine averaged 850 fineness.

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

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

Workings include underground openings comprised of a shaft with extensive workings. The underground workings of the Massachusetts Hill Mine are shown in Figure 44 of U.S. Geological Survey Professional Paper 194 (Johnson, 1940).

Production data are found in: Johnston, William Drumm (1940).

The Massachusetts Hill Mine has reportedly produced $4,078,075 in gold.

Other Databases

Link to USGS MRDS:	10007457

Localities in this Region

Other Regions, Features and Areas containing this locality

References