Sheep Ranch Mine (Washington Mine; Wallace and Ferguson Mine; Chavanne Mine; Pioche Mine; American Mine; Chavanne claim; Wallace claim; McNair claim; Location claim; Aspinwall claim; Northstarv claim; Salamanda claim; Admiral Dewey claim; Rosco claim; Alabama claim; Franklin claim; Lodi claim; Eureka claim; Elk claim; Hurricane claim; Toom claim), Sheep Ranch, Mountain Ranch Mining District, East Belt, Calaveras County, California, USAi

Regional Level Types
Sheep Ranch Mine (Washington Mine; Wallace and Ferguson Mine; Chavanne Mine; Pioche Mine; American Mine; Chavanne claim; Wallace claim; McNair claim; Location claim; Aspinwall claim; Northstarv claim; Salamanda claim; Admiral Dewey claim; Rosco claim; Alabama claim; Franklin claim; Lodi claim; Eureka claim; Elk claim; Hurricane claim; Toom claim)	Mine
Sheep Ranch	Ranch
Mountain Ranch Mining District	Mining District
East Belt	- not defined -
Calaveras County	County
California	State
USA	Country

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A former Au-Ag-Cu-Zn-Fe-Pb mine located in secs. 7, 8, 17 & 18, T4N, R14E, MDM, 0.5 km (1,500 feet/0.3 mile) WSW of Sheep Ranch (5.0 miles due N of Murphys), on private land (Calaveras County Planning Department). Discovered in 1867. The Sheep Ranch Mine was initially known as the Wallace and Ferguson Mine until 1877. After 1877, additional claims were acquired until the Sheep Ranch Mine property encompassed 21 patented claims covering 200 acres. MRDS database stated accuracy for this location is 100 meters.

MRDS file data: The location point selected for latitude and longitude is the main shaft symbol for Sheep Ranch Mine as shown on the USGS Murphys 7.5-minute quadrangle map. The mine is located on private property at the west end of the town of Sheep Ranch. Access is by paved road from Murphys via Sheep Ranch Road or from San Andreas via Fricot City Road to the town of Sheep Ranch, then west approximately a half mile on Main Street to a dead end at the Pioneer Hotel. The mine shaft is located approximately 500 feet to the north.

Surface exposures of a high-grade gold-bearing quartz vein are believed to have been discovered in about 1867 and claimed by C.P. Ferguson and Tom Smith. The original claim was 1600 feet in length by 200 feet wide. Shortly thereafter, W.A. Wallace bought Smith's interest, and during early development the mine was known as the Wallace and Ferguson Mine. Additional claims were added over time. Later these claims would become the main Sheep Ranch Mine. Wallace erected a 5-stamp mill to crush the ore. Using only crude and rudimentary methods, by 1871 they developed the mine to a depth of 94 feet along a quartz vein 8 to 20 inches thick. Ore valued at $34 to $44/ton was treated in arrastras. By 1877, the mine had been developed to 200 feet and had produced approximately $300,000.

In 1877, the Sheep Ranch Mine and claims were acquired by James Ben Ali Haggin (Homestake and Anaconda Mines) and Senator George Hearst (father of William Randolph Hearst). They erected a 20-stamp mill and actively operated the mine as the Sheep Ranch Company until 1893. Development occurred through the main Sheep Ranch shaft to a depth of 1400 feet. During this time the mine was stoped for a length of 1400 feet to a depth of 1300 feet yielding approximately $4,000,000 from 400,000 tons of ore averaging about 0.5 troy ounces per ton. The ore was often so rich in free gold as to yield superb specimen rock. Sulfides in the form of pyrite, chalcopyrite, galena, and sphalerite accounted for less than 0.5% and were not considered worthwhile to retain.

During this period, the competing Chavanne Mining Company developed the Chavanne ore shoot east of the Sheep Ranch main shaft to a depth of 600 feet deep with stoping up to about the 300-level. To avoid litigation regarding claim lines, the Chavanne mine was purchased by the Sheep Ranch Company for $100,000. The Pioche Mine adjoining on the west, with a shaft to 200 feet, was also purchased. From time to time, more adjoining gold-bearing quartz claims covering discoveries on the same vein were acquired until a total of 9 patented claims were owned covering the strike of the vein. In addition to the holding on the main vein, an additional group of claims, several of which are patented, was acquired covering more or less the parallel footwall vein.

High operating costs forced the closure of the mine in 1893. Problems included costly steam-power generation and difficult metallurgy. Wood consumption for steam generation proved to be one of the biggest expenses. In 1888, 12-14 cords of wood were used per day. By 1892, all available timber in the immediate vicinity was consumed resulting in flooding of the mine to the 300 foot level, where a 2500-foot long tunnel drains the mine to the NW into O'Neil Creek.

Amalgamation was the only practicable recovery process available at the time and yielded a recovery of only 75-80% (later operations were able to recover up to 95% by cyanidation).

Reopened in 1898 by W.H. Clary, the Sheep Ranch Mine was deepened to 1,300 feet and operated until 1907. During this period, an east drift on the 1300-foot level found ore extending over twelve hundred feet and was stoped continuously for the full distance as it was on the upper levels. 43,150 tons of ore (worth about $440,000) of an average value of $10.65/ton was mined and milled between 1898 and 1907. Twenty stamps crushed the ore. Amalgamation was used inside the stamp mill battery and on outside plates and sluices with a 80% recovery. Inadequate financing, however, precluded the opening of enough stopes to bring the mill to capacity and profitability.

In 1900, a shaft was commenced on the Lodi claim, one of the Sheep Ranch group, about 700 feet southwest of the main shaft. Whereas, in former years very rich ore was taken from the Lodi vein, no information is available regarding the sinking and development of this shaft.

In 1917, the Monticali Mines Syndicate was formed to explore and evaluate the reopening of the mine. They dewaterd the mine of 50,000,000 gallons and deepened it to the 1700-foot level. In doing so, they discovered rich ore and the Golden Gate Exploration Company was formed to take over operation of the mine. Stoping was largely confined between the 1500- and 1700-foot levels with minor development work on the 1000- and 1400-foot levels. The mill process was converted from amalgamation to cyanidation, which increased recovery to almost 95%. During Golden Gate Exploration's operations, the mine produced 30,832 tons of ore averaging 0.58 oz/ton (or $11.93/ton) resulting in $367,877 (at $20.67/oz for gold). Later, the dump was worked.

Despite the evidence that ore shoots at the lower 1700-foot level were as good as ore elsewhere in the mine, Golden Gate Exploration closed the mine in 1922. Reasons given for closure included incompetent labor, high costs, inadequate equipment for the 1,700 foot depth, scarce and inefficient labor available during the postwar period, and stealing of high-grade ore. Despite the hiring of detectives to thwart it, an estimated at 50% of the mine's production was lost to high-grading, which was considered one of the principle reasons for closure.

The St. Joseph Lead Company reopened the mine in 1936. The mine was dewatered and the mine workings were retimbered and rehabilitated. A new headframe and 180-ton ore bin were erected, and the mill was overhauled. Ore was treated in the 150-ton mill equipped with a 28-inch primary gyratory crusher , a secondary 6 x 6-foot ball mill, Bendelari and Pan-American jigs, flotation cells, and filter presses. The main shaft was deepened to the 2100-foot level and a secondary shaft was sunk to 3,100 feet. Despite promising shows at the 2500-foot level, an east drift at the 2700-foot level encountered very little ore within the projected extension of the ore body. At the 2900-foot level, an east drift was driven 730 feet, but found only massive barren quartz. The mine was deepened to 3,100 feet and drifted to the east in hopes the ore shoot would reappear at depth. Development at the 3100-foot level proved otherwise, and it was concluded the mine had bottomed. The decision to permanently close the mine came in early 1942. During St. Joseph Lead's operation, the mine produced 139,709 tons of ore between 1938-1942. During its final years of operation, gold and silver were recovered from both the ore shoots and limited quantities of sulfide concentrates. Ore values averaged 0.45 ounce/ton gold and 0.055 ounces /ton silver. Concentrates yielded 0.12 ounce gold and 0.02 ounce silver per ton.

The Sheep Ranch Mine has remained idle since its closure in 1942. Shortly after closure, all mine and mill buildings and equipment were dismantled and removed. While there have been proposals to process the remaining tailings in recent decades, none have been implemented on a systematic or significant scale.

Currently, little remains of the Sheep Ranch Mine but overgrown waste rock and tailings piles. A crude wire fence surrounds the open mineshaft. The mine shaft and waste piles are accessible just north of the Pioneer Hotel. The lands are private property and posted. Permission to enter should be obtained before accessing the mine site.

Mineralization is a polymetallic 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 Carboniferous-Triassic rocks of the Calaveras Complex (siliceous and graphitic mica schist). Parallel veins in unnamed fractures. Mineralization occurs as ore shoots within mesothermal gold-bearing quartz veins deposited in parallel fault planes, fractures, and fissures. Ore concentrations are common at intersections of quartz veins and where igneous dikes and quartz veins intersect. Local alteration is negligible (?) - none described. Free-milling native gold is present in quartz veins. Ore has also been highly valued as high-grade specimen material and jewelry-grade gold in blue-black quartz. The very low sulfide content (<0.5%) has never been considered worthwhile to process. Local rocks include Paleozoic marine rocks, undivided, unit 4 (Western Sierra Nevada).

Regional Geologic structures include the Melones Fault Zone, Bear Mountain Fault Zone, Foothills Fault System, and the Calaveras-Shoo Fly Thrust.

The detrital marine sediments of the Calaveras Complex are so severely metamorphosed and deformed at Sheep Ranch that original bedding features have been destroyed. The only recognizable planar element is a strongly defined schistosity striking northwest-southeast and dipping 65-80? to the northeast, and closely paralleling the producing ore veins.

In the Sheep Ranch Mine, the host rock consists of brownish to bluish-black siliceous mica schist and graphitic schist. Intrusive Jurassic granodiorite, diorite, and ultramafic rocks commonly form thin dikes within the schist and are cut by the ore-bearing veins. Veins are usually richer where the veins intersect igneous dikes or where veins intersect one another.

The thickness of the Calaveras Complex has not been determined, but measurements of more then 35,000 feet have been obtained in the Sierra foothills. However, this number does not account for repetition of beds by significant faulting or folding. The extensive reverse faulting and near isoclinal folds associated with the FFS, the well-developed schistosity, and the fractures and shear zones in and near Sheep Ranch all suggest that the true thickness of the Calaveras Complex is much less.

Local structure is difficult to determine due to the destruction of bedding features and marker horizons by metamorphism. The dominant structural feature within the Calaveras Complex rocks at Sheep Ranch is a pronounced schistosity which trends northwest-southeast and dips steeply to the northeast.

The main Sheep Ranch vein strikes N55?W and dips 70-75 (?) NE and is in the hanging wall of a series of at least five known parallel veins. The deposits are considered true fissure filling emplacements resulting from ancillary fractures associated with deeper-seated reverse faulting similar to, but less extensive than, that expressed in the FFS.

Wagner and others (1981) show the Calaveras-Shoo Fly Thrust as passing approximately through the settlement of Sheep Ranch. It was not established from research for this geologic summary, however, if the Sheep Ranch deposit is genetically associated with this structure.

No detailed information exists regarding the extent of wall rock alteration in the Sheep Ranch deposit. It is clear, however, that little significant alteration was ever encountered or exploited as a lower-grade ore. The lack of widespread alteration may be attributable to the nature of the host rock in the Sheep Ranch Mine, which consists almost entirely of siliceous mica schist and graphitic schist.

In contrast, many of the mines in the MLGB and WGB exhibit extensive zones of carbonate alteration in the host rocks. The degree of alteration is often correlative with the mineralogic composition and relative permeabilities of the rocks, with alteration being extensive in metavolcanic and ultramafic rocks and weak in metasedimentary units. Rocks composed of minerals with a high Mg/Fe ratio, such as serpentine, display enhanced fluid permeabilities when in contact with CO2-rich hydrothermal fluids and are much less stable than metasedimentary rocks with low Mg and Fe contents (Landefeld, 1990). An example of this phenomenon is well-displayed in the Royal-Mountain King Mine in the WGB where the correlation between alteration and rock type is pronounced. Alteration of hanging-wall greenstone consists of extensive quartz-sericite-ankerite-mariposite assemblages containing disseminated gold, which extend up to 250 feet from the veins. In contrast, footwall argillite and phyllite display little alteration, which consists of localized pyrite dissemination and bleaching attributed to leaching and remobilization of organic carbon. The predominance of compositionally similar schists in the Sheep Ranch Mine might explain the lack of alteration.

Because there is no known study of the geochemistry of the ore deposit at Sheep Ranch, a summary of some of the regional geochemical conditions is presented as follows:

It is clear from numerous field studies that the gold mineralization of the Mother Lode region took place after the Nevadan Orogeny (approximately 155 Ma). The origin and age of the hydrothermal fluids responsible for the gold mineralization in the Mother Lode region continues to be debated, however (Bohlke, 1999). Similarly, the specific regional tectonic events that stimulated this mineralization have not been conclusively established. A classical interpretation is that the gold-bearing quartz veins were precipitated from aqueous solutions during emplacement of plutons that comprise the Sierra Nevada Batholith. This interpretation lacks, however, specificity regarding the origin of the mineralizing fluids or the source of the contained mineral species. Studies in the areas of tectonic history, plate tectonics, thermodynamics, and geochemistry have advanced, but not conclusively resolved, our understanding of the source of these fluids.

The primary interpretations for the origin of the fluids include metamorphic devolitilization and downward circulating meteoric waters. In places, stable-isotope compositions of hydrothermal minerals and fluid-inclusion characteristics from veins in the Mother Lode are consistent with metamorphic devolitilization in heterogeneous mixed carbonate-silicate rocks at depth, which could have produced a CO2-rich solution. Other studies of fluids extracted from gold-quartz veins in the Mother Lode reveal hydrogen-isotope distributions similar to modern precipitation, suggesting deeply circulating meteoric waters could be largely or partially responsible (Nesbitt and others, 1986). While it is reasonably certain that meteoric water entered the veins at some point, it has not yet been established if it commingled with and comprised a significant fraction of the ascending CO2-rich ore fluids during mineralization or if it entered the veins sometime later.

The origin of the gold and other metallic elements remains problematic (Bohlke, 1999). While not conclusive, hydrothermal experiments and fluid-inclusion studies have suggested aqueous sulfide species may have been responsible for the solubility of the gold, and the low chlorinity and acidity of the fluids may have prevented the dissolution and transport of much larger amounts of the base metals Fe, Cu, Zn, and Pb. If the gold was carried in the form of an aqueous solution of sulfides, it is possible for it to have precipitated from solution in response to various combinations of cooling, mixing, degassing, sulfide precipitation, and increasing or decreasing fluid pH or oxidation state (Seward, 1991). The actual source of the metallic elements is thought to be a variety of rocks below or within the metamorphic cover through which the fluids ascended to sites of mineralization. The contribution from magmatic sources associated with the extensive Sierran plutonism is uncertain.

Direct dating of the Mother Lode veins has been accomplished by Rb-Sr and K-Ar dating of the hydrothermal mica, mariposite, a clearly identifiable product of the carbonate metasomatism associated with the gold veins (Bohlke, 1999). Data summarized by Bohlke and Kistler (1986) for veins in the Melones Fault Zone indicated Early Cretaceous ages between 108 and 127 Ma. These dates have lead various researchers to date mineralization correlative with various major tectonic-plutonic events that occurred around the same time. Many workers have suggested these dates imply a connection with post-Nevadan subduction and arc magmatism. Others have suggested that these dates are too young, arguing that radiometric dates may be younger than initial crystallization ages for minerals subjected to high temperatures (Landefeld, 1990). In either case, mineralization appears to be confined temporally to magmatic activity associated with subduction and associated emplacement of the Late Jurassic-Early Cretaceous plutons associated with the Sierra Nevada batholith.

Workings include underground openings.

The Sheep Ranch Mine is the deepest gold mine of the East Gold Belt. By the time of its closure in 1942, the Sheep Ranch Mine was developed as an underground mine to a depth of 3,100 feet via a 2,100 foot inclined main shaft and a secondary shaft sunk from the 2,100-foot level to the 3,100-foot level. The main shaft is in the hanging wall about 70 feet from the main Sheep Ranch vein, which strikes N55? W and dips 70-75? to the northeast. Ore shoots within the vein rake about 50? to the east.

Drifts were driven along the vein from the main shaft at 100 foot intervals on 22 levels; the maximum length driven on the vein was 2,600 feet. From the 2,100-foot level to the 3,100-foot level, east and west drifts were driven at 200 foot intervals. At the 300-foot level, the Pioche Adit extended 2,500 feet to the west of the shaft and acted as a drain tunnel for the mine. Prior to its operation by the St Joseph Lead Company in 1936, the Sheep Ranch ore shoot was stoped continuously from the 1,300-foot level to the surface averaging 1,400 feet in length, 1,300 feet high, and 5 feet wide. More limited stoping was conducted east and west of the main shaft on the 1,400- through 1,700-foot levels.

West of the main shaft, the Pioche ore shoot was mined from the surface to the 300 foot level where it intersected the Pioche drainage adit.

East of the main shaft, the Chavanne ore shoot was mined from the surface to 600 feet in depth and 400 feet in length. Below 600 feet it was not mined, with the exception of very limited stoping of the 1,300-foot level where an easterly drift from the main shaft cut a poorly mineralized ore shoot 1,400 feet east of the main shaft.

Below the 2,100-foot level, east- and west-trending drifts were driven at the 2,300-, 2,500-, 2,700-, 2,900-, and 3,100-foot levels. The drifts showed declining ore values with depth until the 2,900- and 3,100-foot levels, which encountered barren quartz in the main vein. The mine was subsequently closed.

The Sheep Ranch Mine is considered the most productive gold mine of the East Gold Belt having produced in excess of $7,000,000 in native gold between its opening in the 1860s until final closure in 1942. Ore generally averaged 0.5-0.6 ounces per ton. The most prolific period in the mine's history was between 1877 and 1893 when over 400,000 tons of ore worth over $4,000,000 was produced.

During the bulk of the mine's operation, sulfides in the form of pyrite, chalcopyrite, galena, sphalerite were encountered in concentrations of less than 0.5% and were considered insufficient to warrant the use of concentrators. During the early days of operation, the small amounts of sulfide concentrates collected assayed only $16 - $30 per ton. In the final years of operation, St Joseph Lead recovered less than $4.00 per ton from concentrates.

Upon closure, no significant reserves remained in the known ore shoots. However, the quartz veins persisted at depth, and the presence of undiscovered ore shoots within them is a possibility.

Mineral List

1 valid mineral.