Jamison Mine

Site Name

Primary: Jamison Mine
Secondary: Plumas-Eureka Annex
Secondary: Jamison Ledge
Secondary: Neville Ledge
Secondary: Bosco Ledge
Secondary: South Eureka Ledge
Secondary: Yale Quartz Claim
Secondary: Neville Quartz Claim
Secondary: Harvard Quartz Claim
Secondary: Harvard Annex Quartz Claim
Secondary: Amherst Quartz Claim
Secondary: Amherst-Princeton Extension Claim
Secondary: Plumas Claim
Secondary: Cornell Claim
Secondary: Columbia Claim
Secondary: Princeton Claim
Secondary: Irondik Claim
Secondary: Stanford Claim
Secondary: Vickers Claim
Secondary: Levendol Claim
Secondary: Berkeley Claim
Secondary: Keystone Claim
Secondary: Eureka Lilly Claim
Secondary: Stanford Annex Claim

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Commodity

Primary: Gold
Secondary: Lead
Secondary: Silver
Tertiary: Copper
Tertiary: Arsenic
Tertiary: Iron
Tertiary: Zinc

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Location

State: California
County: Plumas
District: Johnsville District

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Land Status

Land ownership: State Park
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: California Dept. of Parks and Recreation

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Holdings

Not available

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Workings

Not available

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Ownership

Owner Name: California Department of Parks and Recreation

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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
Year First Production: 1887
Year Last Production: 1943
Discovery Year: 1886
Years of Production:
Organization:
Significant: Y
Deposit Size: M

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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, lens

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Structure

Type: L
Description: No significant local structures

Type: R
Description: Melones Fault Zone, Mohawk Valley Fault Zone

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Alterations

Alteration Type: L
Alteration Text: Negligible - None described

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Rocks

Name: Rhyolite
Role: Host
Description: tuffs
Age Type: Host Rock
Age Young: Late Devonian

Name: Tuff
Role: Host
Description: Rhyolite
Age Type: Host Rock
Age Young: Late Devonian

Name: Porphyry
Role: Host
Age Type: Host Rock
Age Young: Late Devonian

Name: Gabbro
Role: Host
Age Type: Host Rock
Age Young: Late Devonian

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Analytical Data

Not available

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Materials

Ore: Chalcopyrite
Ore: Galena
Ore: Sphalerite
Ore: Arsenopyrite
Ore: Gold
Gangue: Quartz

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Comments

Comment (Identification): The Jamison Mine is located just across Jamison Creek about one mile south-southeast of the famous Plumas-Eureka Mine. While the larger Plumas-Eureka lodes were discovered in 1851 and heavily exploited throughout the latter half of the 19th century, it was not until the 1880s that the correlative lodes were discovered on the other side of the canyon near the mouth of Little Jamison Creek. These lodes were developed as the Jamison Mine by the Jamison Mining Company until 1922, when the Jamison Mine was bought by the Plumas-Eureka Annex Mining Company and operated thereafter under that name. Much smaller than the Plumas-Eureka Mine, the Jamison consisted of between 590 and 881 acres and included valuable water rights consisting of four lakes above the mine.

Comment (Location): The location point selected for latitude and longitude is the Jamison Mine site as shown on the USGS Johnsville 7.5-minute quadrangle. The mine is located within the Plumas-Eureka State Park, which is owned and operated by the California Department of Parks and Recreation. Access is via County Highway A14 (Graeagle-Johnsville Road) approximately four miles southwest of Mohawk, California, to the Plumas-Eureka State Park Headquarters and Museum. The Jamison Mine is approximately 1 mile south of the park headquarters via dirt road.

Comment (Development): By 1920, the Jamison Mining Company considered the mine to be uneconomic, and it was leased to local miners Sobrero and Company of Johnsville. The lessees recovered considerable gold by stoping and several additional development drifts. In 1921, the mine was sold to N.M. Srdanovich and the Plumas-Eureka Annex Mining Company for $12,000. Official estimates at the time of sale indicated total production of the Jamison at over $2 million. By 1922, it was recognized that the known reserves were largely exhausted. In 1924, the Plumas-Eureka Annex Mining Company reported holdings of 412 acres patented lode, 300 acres unpatented lode, and 160 acres unpatented placer. The patented property consisted of that portion consisting of the original Jamison Mine. They also asserted that there was enough ore blocked out and assaying between $6 and $16/ton to run the 20-stamp mill for many years, and that a new vein had been opened up that measured 4-14 feet thick and averaged $10/ton. The company never pursued these "claimed" reserves. In June 1925, the mine changed hands again to the Jamison Mining Company, F. J. Behnemen, trustee. Limited development continued between 1925-1927, but little valuable ore was recovered. During this period, 666 feet of drifting and crosscutting was done. An independent report conducted in 1925 concluded that the mine ?as a large operation is concerned? was worked out and the only ore remaining consisted of what little remained after the original Jamison Mining Company ceased operations in 1920. The report also concluded that water was a very serious impediment to further work on the vein or below the drain tunnel level. In 1928, Plumas-Eureka Mining Company took over control again. At this time, the president of the company was trying to promote the property with inflated statements that the mine had produced over $6 million. In the 1930s, the mine passed into the hands of the Carnation Gold Mining Company, Ltd. There are no known records of their operation. During 1941-1943, lessees treated 489 tons of ore and 401 tons of old tailings by amalgamation and concentration and shipped 112 tons of ore and 3 tons of concentrates to a smelter. Amalgamation bullion contained 103 ounces of gold and 13 ounces of silver. Smelted ore yielded 144 ounces of gold and 38 ounces of silver, and concentrates smelted contained 11 ounces of gold and 3 ounces of silver. Mining ceased in 1943. In 1959, the property was acquired by the State of California and incorporated in the newly established Plumas-Eureka State Park.

Comment (Environment): The Jamison Mine (later called the Plumas-Eureka Annex Mine) is located in the Johnsville Mining District of the northern Sierra Nevada about 175 miles northeast of San Francisco. The mine workings are approximately seven miles southwest of the small town of Blairsden in south central Plumas County. The Jamison Mine, along with its more famous contiguous neighbor, the Plumas-Eureka Mine, is within Plumas-Eureka State Park. This area of Plumas County is rural and sparsely populated. The larger communities of Portola and Quincy (Plumas County Seat) are located approximately 14 miles northeast and 20 miles northwest respectively. The small community of Johnsville, which sprung up during the 1800s to support the Plumas-Eureka Mine still exists within the park Its counterpart, Jamison City, no longer exists. Jamison Creek runs northeast through Jamison Canyon and separates Eureka Peak and the Plumas-Eureka Mine from Mt. Washington to the south. The Jamison Mine lies at the northern toe of Mt. Washington in the drainage of Little Jamison Creek. Topography is dominated by heavily forested and mountainous terrain punctuated by small fertile valleys, much of it sculpted by Quaternary glaciation. Several small glacial mountain lakes dot the higher elevations including Grass Lake, Jamison Lake, Wade Lake, and Rock Lake, all upslope of the Jamison Mine. The former mine workings lie at an elevation of 5,350 feet along Little Jamison Creek, 0.5 mile south of its confluence with Jamison Creek. Quartz ledges punctuate the topography, the discovery of which led to the discovery of the Jamison mine. With the exception of the valley floors, which support black oak, the slopes are forested with a mixed conifer forest of ponderosa, sugar, yellow, and red pine; red, white, and douglas fir; and western cedar. In places, barren rock and talus alternate with patches of shrubs that include manzanita, ceanothus, chinquapin, buckthorn, and bitter cherry. Climate is alpine, with average winter low temperatures between 22 - 28oF and summer highs in the mid 80s. Mean annual precipitation is approximately 40 inches, most of which falls during the winter and spring (November to June). Several mine buildings are maintained as park exhibits at both the visitor center and at the site of the Jamison Mine proper. Whereas the focus of exhibits and preserved buildings at the museum relate to the Plumas-Eureka Mine, the visitors center and museum pay tribute to both mines as well as local flora and fauna.

Comment (Commodity): Commodity Info: Free-milling gold-bearing quartz veins with auriferous sulfides. Mineable ores ranged from $4.25 to $16.00/ton. Gold averaged 0.814 fine with secondary silver. Sulfides included pyrite and varying amounts of galena, chalcopyrite, sphalerite, and arsenopyrite. At the nearby Plumas-Eureka Mine, sulfide content ranged from a trace to 1.5%, but reached as much 30% where veins pinched. It is speculated that sulfide content at the Jamison deposit is similar.

Comment (Workings): Because detailed maps and records of the extent of the Jamison Mine's underground workings are not known to be available, it is not feasible to describe the full extent of the workings, especially through the later stages of ownership from 1924 through 1943. According to reports as of 1924, the mine workings consisted of a vertical 3-compartment shaft (manway and 2 hoist shafts) sunk to a depth of 265 feet from collar to sump. Mining was carried on mainly by drifts, cross-cuts, and stopes. There were four levels developed in the mine; the deepest level was an 1,800-foot drain tunnel (Hasken's tunnel), striking S 20? E and intersecting with the main shaft at 165 feet. This tunnel drained the sump and lower level of the mine into neighboring Little Jamison Creek. The three levels above consisted of drifts up to 1,500 feet along two primary gold-bearing veins with crosscuts between them. The veins were stoped between the first and second and second and third levels. The ore from the first, second, and third levels was handled through three ore chutes, which extended through from the first to the fourth level. It was then trammed along the fourth level to the shaft and hoisted to the surface where it was passed through the crushers and to the mill by gravity. Averill (1928) described additional underground exploratory and development work conducted between 1926 and 1928: "Since 1926, a 500-ft. winze has been sunk on the West vein from an upper level, making the bottom 250 ft. below the drain tunnel. At the bottom drifts were run 230 ft. south and 680 ft. north, and an 18-ft. raise was put up from the north drift."

Comment (Geology): Most significant exposed deposits have probably been discovered given the intense scrutiny the area was subjected to during the latter half of the 19th century. However, there are undoubtedly undiscovered deposits in the region. Deposits might exist where the veins do not crop out or where surface exposures do not reflect mineralized ore shoots at depth. Zones of barren quartz commonly separate known ore shoots within veins. More likely would be deposits concealed under the extensive covers of Tertiary volcanic rocks and Quaternary alluvium and glacial debris. GEOLOGY AT THE JAMISON MINE. Rocks of the Sierra Buttes Formation form the bedrock host rocks of the Jamison Mine quartz veins. Locally, they consist of submarine rhyolitic to andesitic tuff interbedded with lenses of black phosphatic radiolarian chert, and siliceous argillite. In the upper part, andesitic tuff and tuff breccia prevail. The Sierra Buttes Formation is highly disrupted by intrusions of gabbro, pyroxenite, quartz porphyry, and diorite. The principal intrusive is gabbro, which carries many of the veins. Elongate inclusions of quartz porphyry are often found within the gabbro and are commonly associated with the veins. Underlying the Sierra Buttes Formation are rocks of the Sierra City Melange Unit of the Shoo Fly Complex. This unit includes the upper Shoo Fly subduction complex, which is composed of blocks of serpentinite, gabbro, basalt, sandstone, limestone, mudstone, and chert within a sheared sandstone and shale matrix. The Sierra Buttes Formation is overlain to the east by the Taylorsville Formation, however, very little of the bedrock is exposed in the immediate vicinity, because it is obscured by extensive and thick glacial alluvium or Tertiary andesite flows. The Jamison ore bodies consist of mineralized shoots within a series of fissure-filling hydrothermal quartz veins much like the typical gold-bearing quartz veins of the California Mother Lode. The veins are of the same type and similar in dips, strikes, and mineral associations as those in the more prolific Plumas-Eureka Mine. They trend northwest-southeast, are roughly parallel but with divergent dips, and cut the various lithologies in the Sierra Buttes Formation: primarily, gabbro, quartz porphyry, and argillite. Typically, veins are a few inches to more than 20 feet thick. Based on records of workings, one of the main veins is at least 1,400 feet long. The primary Jamison Vein strikes N 20? W and dips 20-40? SW and averages 5 feet wide. A peculiar exception is found in the Jamison Vein and some lesser veins where they roll over, become flat, and reverse their dip in an anticlinal form. Where horizontal, these portions of the veins were called floor veins and carry higher gold values. Some veins in the neighboring Plumas-Eureka Mine also display this geometry. While the Jamison Vein was roughly correlated with the vein of the same name in the Plumas-Eureka Mine, complete correlations of the veins between the two mines was never made due to the thick cover of alluvium and glacial debris in the intervening valley. Ore is free-milling quartz vein material and runs about 0.814 fine consisting mainly of gold with little silver (from Plumas-Eureka analyses). The gold is finely divided. The main sections of veins are usually low-value milky bull quartz. Gold values are generally lean in this material and increase along the vein walls. Occasionally, rich ore shoots are found within the veins. The veins also carry minor amounts of auriferous chalcopyrite, galena, sphalerite, and arsenopyrite. One of the noteworthy characteristics of many veins is their good definition, with unbroken walls being traceable for hundreds of feet. In these cases, there is little waste found in the ore due to the regular and clean nature of the walls. However, small amounts of auriferous gouge material sometimes occurred on the foot and hanging walls.

Comment (Geology): Researched documents did not indicate evidence of hydrothermal alteration of the wallrock. While no quantitative information regarding sulfide content in the Jamison Mine is available, it is presumed that sulfides occurred in a manner similar to those at the Plumas-Eureka Mine, where they typically ranged from a trace to 1.5%, but could run as high as 30% where veins pinched.

Comment (Geology): INTRODUCTION The Jamison Mine is located in the Johnsville Mining District in south-central Plumas County. The district is both a lode and placer gold district at the north end of a belt of mineralization extending about 20 miles southward into Sierra County and including the Sierra Buttes Mine ($17-$20 million produced) at its south end. The Plumas-Eureka Mine, which is adjacent to the Jamison Mine, was the largest gold producer in Plumas County having produced between $10 - $15 million. The district is noted for varied exposures of slate, schist, quartzite, metadacite, quartz porphyry, greenstone, and numerous mafic and felsic intrusives. Portions of the district are overlain by Tertiary andesite and/or glacial debris. REGIONAL SETTING The northern Sierra Nevada is home to numerous placer and lode gold deposits and includes many of the more famous gold mining districts such as Grass Valley, Nevada City, Allegheny, Downieville, Eureka, Rich Bar, La Porte, and Johnsville districts. The geological and historical diversity of most of these deposits is covered in numerous publications produced over the years by the U.S. Bureau of Mines, U. S. Geological Survey, California Division of Mines and Geology (now California Geological Survey), and others. Additional information on the geology and history of the Jamison Mine and its more famous neighbor, the Plumas-Eureka Mine, is contained in publications and exhibits available at Plumas-Eureka State Park and in the archives of the Plumas County Museum. The most recent geologic mapping in the area is a 15-minute scale compilation of the Blairsden Quadrangle by Grose (2000). Stratigraphy The northern Sierra Nevada has a history of both oceanic and continental margin tectonics recorded in sequences of oceanic volcanism, near-continental volcanism, and continental volcanism that can be divided into four major lithotectonic belts. These belts are the Western Belt, Central Belt, Feather River Peridotite Belt, and Eastern Belt (Day and others, 1988). The Western Belt is composed of the Smartville Complex, a late Jurassic volcanic arc complex (Beard and Day, 1987). Rocks are basaltic to intermediate pillow lavas overlain by pyroclastic and volcaniclastic rock units with diabase, metagabbro, and gabbro-diorite intrusives. This belt is bounded to the north and east by the Big Bend-Wolf Creek Fault Zone. To the west, it is unconformably overlain by the Cretaceous Great Valley sequence. The Central Belt is bounded to the west by the Big Bend-Wolf Creek Fault Zone and to the east by the Rich Bar and Goodyears Creek faults. The Central Belt is structurally and stratigraphically complex and consists of metamorphosed Mississippian - Triassic chert, argillite, phyllitic argillite, ophiolite, and greenstone of marine origin. It is equivalent to the Calaveras Complex of the central and southern Mother Lode region of the Sierra Nevada. The Feather River Peridotite Belt is also fault bounded, separating highly deformed Central Belt from the rocks of the Eastern Belt for almost 95 miles along the strike of the northern Sierra Nevada (Day and others, 1988). The Feather River peridotite belt consists largely of Devonian to Triassic serpentinized peridotite and dunite.

Comment (Development): The use of these technologies increased efficiencies. In 1897, the Jamison produced $60,000 worth of gold and showed a $25,000 profit. During the first 8 months of the year, with only 10 stamps operating, cost of production was $4.09/ton. With the addition of the second ten stamps the total cost of mining and milling dropped to $2.46. Thus the mine could make a good profit on ores assaying $4.25 -$4.75/ton. In contrast, the Plumas-Eureka Mine became unprofitable at $6/ton. The Jamison Mine also employed a unique assaying system to monitor ore quality. From each working-face carload, a sample was assayed to determine working-face ore values. As each carload reached the top of the shaft, another sample was collected and combined with all. This gave an average assay value of ore for the entire mine and afforded a check on the mill battery samples, which themselves were sampled and assayed every hour. The tailings were also sampled when they left the plates and again after having passed over the concentrators. Thus it was learned what percentage of gold in the mill was being captured and at what points. After leaving the mill, the tailings were flumed to independent arrastras, the company receiving a royalty from them. As of December 1897, the ores averaged $4.25 - $4.75 free gold per ton, with tailings from plates running $1.40-$1.80/ton. Of this, $0.50 - $0.80 per ton was recovered by the concentrators. The concentrator tailings assayed $1.00/ton. About 1000 pounds of sulfides were being recovered daily, which were shipped to the smelter at Selby, California. Aside from its use of available technology, the Jamison Mining Company was noted for its treatment of miners, who by 1898 numbered 35. They were well fed and a boarding house was constructed that offered the luxury of iron beds and spring mattresses. The facilities were described as "unequaled in any mining district" by the Plumas National newspaper. In May, 1899 a fire destroyed the hoist works and mining was suspended until September. The mine reopened with a state-of-the-art sprinkler system and hydrants and an expanded workforce of 60 men. By August 1900 the underground workings had reached the full maturity of development. The mine was worked in three main and several intermediate mining levels. The main crosscut ran westerly for 1,600 feet, developing three veins, two of which were quite profitable, while the third had not yet been thoroughly prospected. Ore was hauled to the shaft and hoisted to the surface. Before leaving the hoisting works, it was dumped over a grizzly, the coarser rock being reduced in an ore crusher before being trammed to the mill and dumped in 450-ton ore bins capable of supplying the mill for a week?s run. At its peak, the Jamison was crushing about 70 tons of ore per day, employed about 60 men and was crushing rock worth $8 - $13/ ton at a total cost of about $2.50/ton Between 1905 and 1908, the Jamison Mine was the leading gold producer in Plumas County. It employed between 50 to 60 men and paid continuous dividends since 1897. However, output was curtailed in 1907 by a water shortage. A reduction in ore values also took its toll, and the work force was cut back. Between 1907 and 1916, operations were reduced to 7 or 8 months a year. Considerable drifting was accomplished in 1908 at which time there were four drift tunnels on the ledges, aggregating 6,473 feet, and one crosscut tunnel of 1,600 feet. From 1915 to 1918, all earnings were used for exploration, with little valuable ore being found. In November 1917, the mine was closed by the State of California until more adequate provisions were made for the storage of the mill tailings. In 1918, the demand for wartime labor and higher wages caused many employees to leave. As a result only ten stamps were run for only 188 days in 1918.

Comment (Economic Factors): Records indicate that the Jamison Mine produced at least $1.4 million by November, 1913. Records are sketchy for the years after 1913, and especially for the years after 1920 when the mine was owned and operated by various lessees and intermittent owners. Official estimates of total production by 1920 were approximately $2.0 million Extravagant claims of up to $6 million were later reported in connection with promotion of the mine for sale. During its early years of operation, ores generally averaged 0.4 - 0.5 ounces per ton. As the efficiencies of technology, ample water power, and the 20-stamp mill came online in 1897, ore assaying as little as 0.2 ounces per ton could be profitably mined and milled. Ore shipped to a smelter as late as 1941, yielded 0.21 ounces per ton. Sulfides generally made up only a small fraction of the ore, and by the early 1900s, concentration and collection of the sulfides were abandoned due to their poor returns. As early as 1915, it became apparent that both the ore values and tonnages were in serious decline. An independent report conducted in 1925 concluded that the mine ?as a large operation can only be considered as a worked out mine.? It is unknown if significant additional ores are present mainly because of the lack of modern exploration and the change in economics of ore bodies. By all accounts of the later history of the mine before its closure, reserves were depleted and efforts to discover new reserves were disappointing.

Comment (Geology): The Eastern Belt, more commonly called the Northern Sierra Terrane, underlies the Johnsville District and is separated from the Feather River Peridotite Belt to the west by the Melones Fault Zone. To the east are the Mesozoic plutonic granitic rocks of the Sierra Nevada Batholith. The Northern Sierra Terrane is primarily composed of Devonian to Jurassic metavolcanic rocks and the earlier Shoo Fly Complex. The Shoo Fly Complex is a sequence of siliclastic metasedimentary basement rocks of continental origin. The dominant provenance of Shoo Fly sedimentation was the North American continental crust. The Shoo Fly Complex also contains shale- matrix melanges containing serpentinite, limestone, phyllite, and chert that developed in a trench setting. Unconformably overlying the Shoo Fly Complex is a series of three superimposed upper Devonian to Jurassic island-arc sequences (Brooks, 2000). The earliest volcanism is recorded in the upper Devonian - Pennsylvanian (?) Taylorsville Sequence, which includes the Grizzly, Sierra Buttes, Taylor, and Peale Formations. Later episodes of volcanism are preserved in the Permian - Triassic Arlington, Goodhue, and Reeves Formations and the Jurassic volcanic rocks of the Sailor Canyon Formation. In the area of the Jamison Mine, only the older rocks of the Shoo Fly Complex, Sierra Buttes Formation, and Taylor Formation are exposed where not obscured by extrusive Tertiary volcanic rocks or later Quaternary alluvium and glacial debris. Rocks of the Peale Formation and later island-arc sequences occur farther northeast. The Taylorsville Sequence consists of submarine volcanic and volcaniclastic rocks and radiolarian chert of the Grizzly, Sierra Buttes, and the lower member of the Peale Formation. The Grizzly Formation is present only locally along the unconformity between the Shoo Fly Complex and the Sierra Buttes Formation. Near its type location, the Sierra Buttes Formation consists of four major units. The lower three units are primarily rhyolitic to dacitic in composition. The upper unit is primarily andesitic. All four units contain thick, discontinuous beds of lapilli tuff, tuff breccia, tuffaceous turbidites, and argillite with interbeds of carbonaceous and phosphatic chert, and laminated tuff (Hanson, 1983) intruded by rocks ranging from gabbro to rhyolite. Hanson interpreted these deposits to be submarine mass-flow deposits produced by eruption or slumping of near-vent accumulations within a volcanic island-arc sequence. The Sierra Buttes Formation is conformably overlain by andesitic submarine volcanic and volcaniclastic rocks of the Taylor Formation. It consists primarily of andesite breccia, massive and pillowed andesite and basaltic andesite flows, and andesitic volcaniclastic turbidites. Overlying the Taylor Formation is the Peale Formation, which consists of a lower volcanic-volcaniclastic member and an upper chert member. The lower member contains massive trachytic to quartz latite flows, tuff breccia, tuff, tuffaceous siltstone, and sandstone (Harwood, 1988) and grades upward into siltstone, sandstone, and limestone. The lower member grades abruptly into a thin bedded black, red, green, and gray radiolarian chert member that serves as a widespread marker unit in the region. The Peale Formation records the waning stages of Late Devonian and Early Mississipian submarine arc volcanism (Grose, 2000). The chert member, which includes bedded radiolarian chert and other pelagic and siliceous sediments, reflects regional subsidence of the volcanic arc to abyssal ocean depths.

Comment (Commodity): Ore Materials: Native gold, chalcopyrite, galena, sphalerite, arsenopyrite

Comment (Commodity): Gangue Materials: Quartz; fault gouge

Comment (Geology): Regionally, the northern Sierra basement rocks are overlain by a series of Tertiary volcanic and sedimentary rocks of mostly Miocene and Pliocene age. The oldest of the Tertiary units in the area is a basal conglomeratic unit commonly referred to as Eocene auriferous gravels. The gravels are preserved in paleochannels eroded in the basement surface. In contrast to the earlier volcanism, Tertiary volcanism was continental and deposited on top of the eroded island arc rocks and Mesozoic intrusives. As many as eight different volcanic units blanket large portions of the area ranging from the lower Lovejoy Basalt to widespread andesitic flows and breccias. The youngest deposits include Quaternary sediments. Extensive beds of Quaternary alluvium and Quaternary morainal and glaciofluvial debris blanket much of the region. Structure Most upper Jurassic and earlier rocks of the northern Sierra Nevada were metamorphosed and deformed during the Jurassic-Cretaceous Nevadan Orogeny (Clark, 1960), the primary expression of the Jurassic amalgamation of oceanic terranes with the Mesozoic continental margin (Moores, 1972; Saleeby, 1981; Schweickert and Cowen, 1975). The dominant northwest trending structural grain of the Northern Sierra Terrane is a result of this period of compressive deformation, which produced east-directed thrust faults, major northwest-trending folds, and regional greenschist facies metamorphism (Harwood, 1988). This episode also resulted in many of the intrusions of granitic plutons that formed the Sierra Nevada. However, all the main lithotectonic belts of the northern Sierra Nevada also contain rocks that have undergone significant pre-Nevadan deformation and metamorphism. While the nature and extent of pre-Nevadan deformation is poorly understood, the principal expression of this earlier deformation is a cleavage or metamorphic foliation that dips steeply and strikes north-northwest (Day and others, 1988). Nevadan deformation structures within the northern Sierra Nevada lithotectonic blocks are steeply dipping, northwesterly trending faults and folds. These faults are best developed in the Eastern, Central, and Feather River Peridotite Belts, where they have been collectively described as the "Foothills Fault System" (Clark, 1960). They deform upper Jurassic rocks and are truncated by uppermost Jurassic and Cretaceous plutons. Where the attitude can be determined, most of the bounding faults dip steeply east and display reverse displacement. Significant structural deformation in the area was absent from the end of the Cretaceous to the Pliocene or Quaternary. Two fault zones of Pliocene(?) and Quaternary age occur in the area. The Mohawk Valley Fault Zone, which lies to the east of the Jamison Mine, trends north-northwest, is normal and down to the west, and suggests over 1,000 feet of dip-slip displacement with a minor right slip component (Jennings, 1994). The Mohawk Valley Fault Zone has been ascribed as the eastern front of the Sierra Nevada, but more likely represents a zone within the Sierra Nevada that is transitional to the Basin and Range province (Grose, 2000). The Grizzly Valley Fault Zone is northeast of the Mohawk Valley Fault Zone and strikes northwesterly. About a mile wide, the zone is composed of down-to-the-west, left-stepping, high-angle normal faults with estimated dip-slip displacement of a few hundred feet. Metallogeny The northern Sierra Nevada harbors many individual mining districts, each known for important deposits of lode and/or placer gold. Lode gold occurs primarily as native-gold ore shoots within hydrothermal quartz veins and, to a lesser degree, in low-grade altered wall rocks.

Comment (Development): In the latter half of the 1880s, just as the neighboring Plumas-Eureka Mine's fortunes were declining, gold-bearing quartz ledges were found 2 miles south on Little Jamison Creek. These ledges became known as the Jamison, Nevill, and Bosco (or South Eureka) ledges. The ledges lay in a direct line with the best ores mined at the Plumas-Eureka Mine and it quickly became apparent that the geology and character of the ore was the same, including the direction and dips of the veins. Complete correlation of the veins, however, was never made due to the thick overlying mantle of intervening morainal material. Upon learning of the discovery, San Francisco capitalists incorporated the Jamison Mining Company on January 19, 1887. Before commencing operations, the company had to go to court to secure title to 590 acres of claims covering the ledges. The company also acquired the water rights to Rock Lake, Jamison Lake, Wades Lake, and Grass Lake above the mine to provide ample water power. Operations were modest at first. A 400-foot tunnel was driven along the main vein to make sure the vein was rich, and ores were worked the first few years in arrastras. This early phase involved working a six-foot wide vein that yielded ore at approximately $8/ton. By 1891, the mine was worked through a 165-foot triple compartment shaft (manway and two hoist shafts), connecting at the bottom with an 1800-foot tunnel that ran 800 feet along the vein and served as the main drain tunnel, which discharged to Little Jamison Creek. Each shaft compartment was 5 feet by 6 feet. Two were used for hoisting, the other for pumping. Unlike those in the Plumas-Eureka Mine, the quartz veins were near or below the creek level and couldn't be accessed by tunnels alone. Later, the shaft was deepened to 265 feet to act as a drainage sump and an electrically operated pump was installed at the bottom to pump the water up to the drain tunnel. Finally convinced of the mine's richness, in 1896 the Jamison Mining Company constructed a 10-stamp quartz mill, the stamps having been purchased from the waning Plumas-Eureka Mine. In 1897, 10 more stamps were added for a total of 20, capable of crushing 60 tons per day. Four concentrators were installed to handle the tailings. Remaining tailings were flumed to arrastras 0.5 mile away on Jamison Creek. These arrastras are reported to have operated until the 1920s. Water was diverted from the lakes above the mine site. All four lakes naturally discharged through Grass Lake from which water was conveyed through a 1-?-mile-long ditch and pipeline to power the mine and mill. Water discharged at the hoist under a head of 460 feet and at the mill's Pelton wheels under a head of 525 feet. By 1898, 7 Pelton wheels were used to run the hoist, compressor, mill, electric light dynamo, rock crusher, shaft lighting, and most shop equipment. To prevent flooding of the underlying mine workings, a 1,000-foot-long, 12-foot-wide flume also had to be constructed to divert the course of Little Jamison Creek where it flowed over a valuable portion of the mine. By the 1890s, mining methodologies at the Jamison Mine were far superior to those used at the Plumas-Eureka Mine. New technologies, tools, and better business practices allowed much more efficient extraction and processing of ores. Pneumatic drills had replaced hammer and chisel allowing for faster and deeper holes for blasting. Dynamite replaced black powder. These advances permitted speedier digging, and larger and better-controlled blasting. The Pelton wheels also allowed electric lighting in the tunnels and mine buildings, which proved to be much safer and cheaper than oil lighting. Even formerly manual operations such as sawing had been replaced by electrified circular saws for timbering, etc.

Comment (Deposit): After the decline in fortunes of the larger neighboring Plumas-Eureka Mine, the Jamison Mine became the leading gold producer in Plumas County. It also had the distinction of being the most efficient mine in the county due to its use of new technology and plentiful water power. In its heyday, it consisted of over 500 acres of claims and controlled the timber and water rights upslope of the mine between Mt. Washington and Mt. Elwell. The Jamison gold deposits occur in fissure-filling hydrothermal quartz veins within metavolcanic island-arc rocks of the Lower Devonian Sierra Buttes Formation. They appear to be a roughly correlative southern extension of the system of mineralized veins in the Plumas-Eureka Mine. The veins cut several lithologies including gabbro, pyroxenite, quartz porphyry, diorite, and rhyolitic tuff. During the upper Jurassic Nevadan Orogeny, much of the Sierra Nevada was metamorphosed and folded into a complex series of parallel northwest trending folds and reverse fault complexes, arguably the most famous of which is the Melones Fault Zone. The Melones Fault Zone forms the western boundary of the Northern Sierra Terrane, one of four major lithotectonic blocks in the northern Sierra Nevada, and within which the Jamison Mine is located. During and shortly after this upheaval, low-sulfide, native gold-bearing hydrothermal veins were emplaced throughout much of the western Sierra Nevada. Two primary vein systems occur in the Jamison Mine and have been variously described as the old (Jamison) and new veins, or east and west veins in the literature. Gold is finely divided, and the ore free-milling. Fineness is approximately 0.815. The veins are roughly parallel and generally trend NNW-SSE. Dips are variable, especially in the Jamison vein where dips flatten and roll over into an anticlinal form yielding areas of almost horizontal veining. The quartz is typically milky white bull quartz. Gold values are low in this material and generally increase towards the vein walls, where veins thin, and where veins flatten. Based on the similar geologic setting, age, and mineral assemblages, the Jamison veins are thought to be mesothermal deposits contemporaneous with other veins in the Sierra Nevada that have been documented as mesothermal. Fluid inclusion and paragenetic mineral assemblage studies in the Alleghany District of the northern Sierra Nevada (Coveney, 1981) are consistent in placing mineralization temperatures of quartz veins there at between 200? - 325?C and pressures up to 2.5 kilobars. Unlike many important mines in the Sierra Nevada, records and descriptions of the Jamison Mine suggest little alteration of the wall rock with the exception of relatively thin gouge zones bordering the veins.

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References

Reference (Deposit): Schweickert, R. A. and Cowan, D. S., 1975, Early Mesozoic tectonic evolution of the western Sierra Nevada, California: Geological Society of America Bulletin, v. 86, p. 1329-1336.

Reference (Deposit): Silva, S. R. and others, 2000, Devonian Sierra Buttes Formation in the Jamison Lake area: Involvement of ancient continental crust in magma genesis, in Brooks, E. R. and Dida, L.T., editors, Field guide to the geology and tectonics of the northern Sierra Nevada: California Division of Mines and Geology Special Publication 122, p. 16-52.

Reference (Deposit): Jackson, W. T., 1961, A history of mining in the Plumas-Eureka State Park area: Unpublished report prepared for the State of California, Division of Beaches and Parks, 36 p. (available for reference at the Sacramento Library of the California Geological Survey).

Reference (Deposit): Day, H. W. and others, 1988, Metamorphism and tectonics of the northern Sierra Nevada, in Ernst, W. G., editor, Metamorphism and crustal evolution of the western United States (Rubey Volume VII): Prentice-Hall, Englewood Cliffs, New Jersey, p. 738-759.

Reference (Deposit): Girty, G. H. and Schweickert, R. A., 1984, The Culbertson Lake allochthon, a newly identified structure within the Shoo Fly Complex, California - Evidence for four phases of deformation and extension of the Antler orogeny to the northern Sierra Nevada: Modern Geology, v. 8, p. 181-198.

Reference (Deposit): Grose, T.L.T. and others, 2000, Geologic map of the Blairsden 15' quadrangle, Plumas County, California, California Division of Mines and Geology Open-File Report 2000-21, scale 1:62,500.

Reference (Deposit): Hamilton, F., 1919, Plumas County: California State Mining Bureau 16th Annual Report of the State Mineralogist, p. 21-27, 136.

Reference (Deposit): Hanson, R. E., 1983, Volcanism, plutonism and sedimentation in a late Devonian submarine island-arc setting, northern Sierra Nevada, California: Columbia University, Ph.D dissertation, 345 p.

Reference (Deposit): Hamilton, F., 1922, California State Mining Bureau, 18th Report of the State Mineralogist, p. 604.

Reference (Deposit): Clark, L. D., 1960, Foothills fault system, western Sierra Nevada, California: Geological Society of America Bulletin, v. 71, p. 483-496.

Reference (Deposit): Clark, L. D., 1964, Stratigraphy and structure of part of the Sierra Nevada metamorphic belt, California: U.S. Geological Survey Professional Paper 410, 70 p.

Reference (Deposit): Clark, W. B., 1970, Gold districts of California: California Division of Mines and Geology Bulletin 193, p. 82-83.

Reference (Deposit): Coveney, R. M., Jr., 1981, Gold quartz veins and auriferous granite at the Oriental Mine, Alleghany, California: Economic Geology, v. 76, no. 8, p. 2176-2199.

Reference (Deposit): Crawford, J. J., 1894, Plumas County: California State Mining Bureau 12th Annual Report of the State Mineralogist, p. 217.

Reference (Deposit): Crawford, J. J., 1896, Plumas County: California State Mining Bureau 13th Annual Report of the State Mineralogist, p. 298.

Reference (Deposit): Harwood, D.S., 1988, Tectonism and metamorphism in the northern Sierra Terrane, northern California, in Ernst, W. G., editor, Metamorphism and crustal evolution of the western United States (Rubey Volume VII): Prentice-Hall, Englewood Cliffs, New Jersey, p. 764-788.

Reference (Deposit): Irelan, W., 1888, Plumas County: California State Mining Bureau 8th Annual Report of the State Mineralogist, p. 476-478.

Reference (Deposit): McMath, V. E., 1958, The geology of the Taylorsville area, Plumas County, California: University of California, Los Angeles, Ph.D dissertation, 199 p.

Reference (Deposit): D'Allura, J. A., 1977, Stratigraphy, structure, petrology, and regional correlations of metamorphosed upper Paleozoic volcanic rocks in portions of Plumas, Sierra, and Nevada counties, California: University of California, Davis, Ph.D dissertation, 338 p.

Reference (Deposit): Day, H. W., 1985, Structure and tectonics of the northern Sierra Nevada: Geological Society of America Bulletin, v. 96, p. 436-450.

Reference (Deposit): Moores, E. M., 1972, Model for a Jurassic island arc - continental margin collision in California: Geological Society of America Abstracts with Programs, v. 4, no. 3, p. 202.

Reference (Deposit): Saleeby, J., 1981, Ocean floor accretion and volcanoplutonic arc evolution of the Mesozoic Sierra Nevada, in Ernst, W. G., editor, The geotectonic development of California (Rubey Volume I): Prentice-Hall, Englewood Cliffs, New Jersey, p. 132-181.

Reference (Deposit): Averill, C. V., 1928, Plumas County: California Division of Mines 24th Annual Report of the State Mineralogist, p. 261-269, 293.

Reference (Deposit): Beard, J. S. and Day, H. W., 1987, The Smartville intrusive complex, Sierra Nevada, California: The core of a rifted volcanic arc: Geological Society of America Bulletin, v. 99, no. 6, p. 779-791.

Reference (Deposit): Bradley, W. W., 1937, Mineral resources of Plumas County: California Journal of Mines and Geology, v. 33, no. 1, p. 79-89, 112.

Reference (Deposit): Brooks, E. R., 2000, Geology of a late Paleozoic island arc in the Northern Sierra terrane, in Brooks, E. R. and Dida, L.T., editors, Field guide to the geology and tectonics of the northern Sierra Nevada: California Division of Mines and Geology Special Publication 122, p. 53-110.

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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.