New York Hill Mine

Site Name

Primary: New York Hill Mine

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Commodity

Primary: Gold
Secondary: Silver

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Location

State: California
County: Nevada
District: Grass Valley

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Land Status

Land ownership: Private
Note: the land ownership field only identifies whether the area the mine is in is generally on public lands like Forest Service or BLM land, or if it is in an area that is generally private property. It does not definitively identify property status, nor does it indicate claim status or whether an area is open to prospecting. Always respect private property.
Administrative Organization: Nevada County Planning Department

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Holdings

Not available

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Workings

Not available

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Ownership

Not available

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Production

Not available

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Deposit

Record Type: Site
Operation Category: Past Producer
Deposit Type: Hydrothermal vein
Operation Type: Underground
Discovery Year: 1852
Years of Production:
Organization:
Significant: Y

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Physiography

Not available

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Mineral Deposit Model

Model Name: Low-sulfide Au-quartz vein

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Orebody

Form: Tabular

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Structure

Type: R
Description: Wolf Creek Fault Zone, Gillis Hill Fault, Melones Fault Zone

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Alterations

Alteration Type: L
Alteration Text: Ankeritic, sericitic, and pyritic replacement of wall rocks adjacent to veins

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Rocks

Name: Diabase
Role: Host
Age Type: Host Rock
Age Young: Mesozoic
Age Old: Paleozoic

Name: Granodiorite
Role: Host
Age Type: Host Rock
Age Young: Early Cretaceous

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Analytical Data

Not available

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Materials

Ore: Gold
Ore: Pyrite
Ore: Galena
Gangue: Quartz
Gangue: Calcite
Gangue: Chalcopyrite
Gangue: Sphalerite

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Comments

Comment (Development): The New York Hill vein was one of the earliest to be mined in the district. The early work on the vein was done through the Chevanne and New York Hill shafts. On the 400-foot level, the vein was followed for 2,000 feet on the strike. It was stoped for 600 feet down dip in the Chevanne workings and 1,300 feet down dip in the New York Hill shaft. Between 1852 and 1865, it produced $500,000, and in 1866-67, 2,189 tons of ore yielded $106,430, an average of $49 per ton. Shortly thereafter, mining was suspended. Mining resumed in 1874 when it was reopened by means of a tunnel from Wolf Creek. The vein produced $100,000 between September 1874 and October 1875. In 1882, ore averaged $25/ton. In 1894, the North Star Mine purchased the New York Hill Mine. After about 6,000 tons of ore were removed, the mine was again closed and had not been reopened as of the late 1930s (Johnston, 1940). It is estimated that the New York Hill Mine produced about $1,500,000 from 100,000 tons of ore before closure. In 1929, the Newmont Mining Co. purchased a controlling interest in the North Star properties, which were consolidated with their Empire Mine as the Empire-Star Mines Co., LTD.

Comment (Economic Factors): It has been estimated that the New York Hill Mine produced $1,500,000 from 100,000 tons of ore between 1852 and its closure in 1894.

Comment (Geology): An important structural feature in the district is a group of "crossing" vertical or steeply dipping fractures that strike northeast, about normal to the long axis of the granodiorite body. In places they are simple fractures; elsewhere they form sheeted fracture zones several feet wide. Some are tight, some are open and form watercourses, and few contain any quartz. Two main stages of primary or hypogene mineralization are recognized - 1) a hypothermal stage represented by one vein and one mineralized crossing, in which magnetite, pyrrhotite, pyrite, and specularite were deposited, and 2) a mesothermal stage, in which the gold quartz veins were formed. The mesothermal stage is further divided into two sub-stages - an older one, in which quartz is the principal gangue mineral, and a younger one, marked by the deposition of carbonates. Pyrite and arsenopyrite, deposited in the quartz stage, are the earliest sulfides of the gold-quartz veins. Sphalerite, chalcopyrite, and galena are somewhat later. No secondary or supergene minerals have been noted except limonite, calcite, and gypsum, which are being deposited in the oxidized zone. The distribution of gold in the ore shoots is extremely erratic and assays of adjacent vein samples commonly differ widely. Some ore shoots have a pitch length of several thousand feet, but most are much smaller. Adjacent to veins and crossing fractures, the wall rocks are generally highly altered. Ankerite, sericite, and pyrite have replaced the original rock-forming minerals. Lesser amounts of chlorite and epidote have been found. The wall rock has not been replaced by quartz. LOCAL GEOLOGY The New York Hill vein strikes N 55? W and dips an average of 33? NE. The vein belongs to the North Star system of veins that produced in the famous North Star Mine located to the south. In general, the New York Hill vein is more uniform in width and structure and has fewer splits and divergent walls than either the North Star or other veins in the North Star vein group. In the older shallow workings, the thickness of the vein ranged from 8 inches to 2 feet, but swelled to as much as 3 feet on the 600-foot level. The quartz is subhedral, in places has comb structure, and shows little evidence of shearing. In the lower levels, the vein fracture is generally narrow, and the average width of the quartz-vein filling is 6-12 inches, with a maximum of 24 inches. The outline of the ore shoots are shown in Johnson (1940, pl. 30). In the upper stopes, the quartz contained 2-3 percent sulfides, which yielded 4-5 ounces ($80-$100) of gold per ton. Most of the gold was free and much of it was coarse specimen gold. Below the 600-foot level, the quartz was too narrow to allow profitable mining.

Comment (Location): The location point selected for latitude and longitude represents the New York 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

Comment (Geology): REGIONAL GEOLOGY The New York Hill Mine is within the Grass Valley District, home to California's two largest underground gold mines, the Empire and the Idaho-Maryland. The district is located in the northern portion of the Sierra Nevada Foothills Gold Belt. This belt averages 50 miles wide and extends for about 150 miles in a north-northwest orientation along the western slope of the Sierra Nevada range. The Foothills Gold Belt roughly coincides with the Foothills Metamorphic Belt, which can be subdivided into four major lithotectonic belts: Western Belt, Central Metamorphic Belt, Feather River Peridotite Belt, and Eastern Belt. The Grass Valley District lies within the Central Belt, where in the Grass Valley area it is marked by an 8-mile-wide north-trending assemblage of two accreted terranes that range from Late Triassic to Late Jurassic in age. The Central Belt is bounded on the east and west by regional-scale tectonic suture zones; the Wolf Creek Fault Zone on the west and the Gills Hill Fault/Melones Fault Zone on the east. The oldest rocks in the area are those of the Carboniferous-Triassic metasedimentary Calaveras Complex. Originally clastics, these rocks were converted to schistose or slaty rocks during the Late Paleozoic orogeny and locally into a contact-metamorphic biotite gneiss by intruded granodiorite during Late Mesozoic time. The slates of the Jurassic Mariposa Formation, which outcrop in a small part of the area, are relatively unaltered. Igneous rocks in the district include granodiorite, diabase, porphyrite, amphibolite schist, serpentinite, gabbro, diorite, quartz porphyry, and various dike rocks (Johnston, 1940). The veins of the Grass Valley and neighboring Nevada City districts are not connected with or continuations of the famous Mother Lode vein system to the south. The last veins of the Mother Lode end about 20 miles to the south. Also, the Grass Valley veins differ in general character from those of the Mother Lode. Generally, the Grass Valley veins are narrower and produce a higher-grade ore than those of the Mother Lode. The veins trend in two primary directions. One set trends N-S (dipping E or W), and the other trends E-W (dipping N or S). The major feature of the Grass Valley District is a body of Lower Cretaceous granodiorite and diabase five miles long from north to south and half a mile to two miles wide (probably the apex of a larger batholitic mass). It which is intruded into older sedimentary and igneous rocks, including diabase of the Mesozoic-Paleozoic Lake Combie Complex, and is itself cut by various dike rocks. Gold-quartz veins cut the granodiorite and diabase (and in some cases, serpentinite) throughout the district. Most of the veins strike generally north, parallel to the intrusive body, and display gentle dips averaging 35?. Others strike northwest, parallel to a diabase contact with the granodiorite. The veins fill minor thrust faults that occur within fracture zones of various width and degree of fracturing. The maximum measured reverse displacement is 20 feet (Johnston, 1940). In all veins, quartz is the principal vein material and occurs in four textural types: 1) Comb quartz that forms crustifications and lines vugs, 2) massive milky quartz with a granular texture that displays many sharp crystal faces and has not undergone deformation, 3) sheared quartz developed with little or no dilation of the vein fracture and commonly showing ribbon or shear-banding structures, and 4) brecciated quartz formed where vein movement dilated the interwall space (Johnston, 1940). Gold occurs in quartz and in sulfides, principally pyrite. Although specimen ore has been found, most ore from the district occurs as fine and coarse free-milling gold in ores averaging between 0.25 to 0.5 ounces per ton.

Comment (Workings): Portions of the New York Hill underground workings through 1940 are shown in Johnson (1940, fig. 53 and pl. 30).

Comment (Commodity): Ore Materials: Free-milling coarse and fine gold in quartz (850 fine). Auriferous pyrite and galena.

Comment (Commodity): Gangue Materials: Quartz, calcite, chalcopyrite, sphalerite

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References

Reference (Deposit): Clark, W.B., 1970, Gold districts of California: California Division of Mines and Geology Bulletin 191, p. 53.

Reference (Deposit): Johnston, W.G., Jr., 1940, The gold quartz veins of Grass Valley, California: U.S. Geological Survey Professional Paper 194, 101 p.

Reference (Deposit): Koschmann, A.H., and Bergendahl, M.H., 1968, Gold-producing districts of the United States: U.S. Geological Survey Professional Paper 610, 283 p.

Reference (Deposit): Lindgren, W., 1896a, Geologic atlas of the United States - Nevada City Special Folio: U.S. Geological Survey Folio 29.

Reference (Deposit): Lindgren, W., 1896b, Gold-quartz veins of Nevada City and Grass Valley: Seventeenth Annual Report of the U.S. Geological Survey, Part 2, p. 1-262

Reference (Deposit): MacBoyle, E.M., 1919, Mines and mineral resources of Nevada County: Sixteenth Annual Report of the State Mineralogist, California State Mining Bureau, p. 1-270.

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