Diamond - Bullion - Alaska

Site Name

Primary: Diamond - Bullion - Alaska
Secondary: Consolidated Bullion Mine
Secondary: Diamond claim
Secondary: Bullion claim
Secondary: Alaska claim
Secondary: Union Jack claim
Secondary: Galena claim
Secondary: Ione claim

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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 Dept.

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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: 1865
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 and sericitic 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
Ore: Calcite
Ore: Chalcopyrite
Ore: Sphalerite
Gangue: Quartz

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Comments

Comment (Geology): REGIONAL GEOLOGY The Diamond, Bullion, and Alaska mines are 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 (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 Diamond, Bullion, and Alaska claims covered three principal veins on the western flank of Osborn Hill, the Big Diamond, Galena- Bullion, and Alaska veins. The veins strike northwest and dip 45? easterly. Since they are roughly in line with one another, they were considered segments of a continuous vein system. Estimates of production from theses veins range as high as $3,500,000. More mining was done on the Galena-Bullion vein than on any others of this group. The vein has an easterly dip of about 33?, varies in width from 1 to 5 feet and carries free gold, pyrite, and a considerable amount of galena. The sulfides average 4% and are valued at $75 per ton. Ore values averaged $20 per ton of 815 fine gold. The Big Diamond vein strikes N 20? W and like the Galena-Bullion vein, of which it is the northerly extension, dips 45? east. The vein is 2 feet wide and produced an average of $20 per ton. The Little Diamond is an east-west vein dipping 48? S that crosses the Big Diamond vein. The Alaska vein is the southern extension of the Galena-Bullion vein and is similar to it in all respects.

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

Comment (Economic Factors): The Diamond, Bullion, and Alaska veins reportedly produced $3,500,000 in gold.

Comment (Development): These claims cover three principal veins on the western flank of Osborn Hill, the Big Diamond, Galena- Bullion, and Alaska veins. The claims were operated as individual mines until later consolidation brought them under single ownership. The Bullion Mine was first worked in the 1860s. It later acquired the Diamond Mine, which is located about 2500 feet northwest of the Bullion shaft. The mine was closed for much of the late 1800s but was reopened in the early 1900s, closing again in 1906. The Alaska Mine adjoins the Bullion mine to the south and is on the southern extension of the Bullion vein. It was worked periodically until 1916. In 1933, the Consolidated Bullion, Inc., consolidated and reopened these mines. While little information is available it is assumed the mines operated until 1942 when enactment of the Federal War Production Board's Limitation Order L-208 closed the few remaining mines that were operating in the Grass Valley District.

Comment (Location): The location point selected for latitude and longitude represents the approximate boundary line between the Bullion and Alaska claims shown 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 (Workings): The Bullion Mine was developed to a depth of 1500 feet by means of an inclined shaft, which, starting in the hanging wall, encountered the vein at a depth of 300 feet then followed the vein. Levels were run as follows: 300- and 400-foot levels both driven 150 feet north and south of the shaft; 600-foot level driven 150 feet north; 700-foot level driven 300 feet north and 300 feet south; 900-foot level driven 250 feet south; 1000-foot level driven 500 feet north; 1100-foot level driven 700 feet north, and a 1500-foot level driven 750 feet north and south of the shaft. A crosscut was also driven from a point 200 feet south on the 900-foot level a distance of 150 feet west into the footwall of the vein (MacBoyle, 1919). In the Diamond Mine, the vein was developed by a vertical shaft and an inclined shaft 290 feet deep. A 1000-foot tunnel was also driven on the vein. The deepest workings below the outcrop are about 125 feet deep, but 1200 feet of exploratory drifts have been driven on the vein, which varies in width from 1.5 to 3 feet wide (MacBoyle, 1919).

Comment (Commodity): Ore Materials: Free milling fine and coarse gold in quartz - 815 fine. Auriferous pyrite and galena.

Comment (Identification): The Diamond, Bullion, and Alaska mines, located on the west flank of Osborn Hill approximately 1.5 miles south of the famous Empire Mine, were consolidated and operated by Consolidated Bullion, Inc. Total production has been reported to be approximately $3,500,000.

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References

Reference (Deposit): Additional information on the Bullion Mine is contained in File No. 339-3114 (CGS Mineral Resources Files, Sacramento)

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.

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.

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California Gold

"Where to Find Gold in California" looks at the density of modern placer mining claims along with historical gold mining locations and mining district descriptions to determine areas of high gold discovery potential in California. Read more: Where to Find Gold in California.