Wildman Mahoney Mine

Site Name

Primary: Wildman Mahoney Mine

---

Commodity

Primary: Gold
Secondary: Silver

---

Location

State: California
County: Amador
District: Sutter Creek

---

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: Amador County Planning dept.

---

Holdings

Not available

---

Workings

Not available

---

Ownership

Not available

---

Production

Not available

---

Deposit

Record Type: Site
Operation Category: Past Producer
Deposit Type: Hydrothermal vein
Operation Type: Underground
Discovery Year: 1851
Years of Production:
Organization:
Significant: Y

---

Physiography

Not available

---

Mineral Deposit Model

Model Name: Low-sulfide Au-quartz vein

---

Orebody

Form: Tabular, pinch and swell

---

Structure

Type: R
Description: Bear Mountains Fault zone, Melones Fault zone

Type: L
Description: Melones Fault Zone

---

Alterations

Alteration Type: L
Alteration Text: Ankeritic and sericitic alteration of wall rocks

---

Rocks

Name: Amphibole Schist
Role: Host
Age Type: Host Rock
Age Young: Late Jurassic

Name: Greenstone
Role: Host
Age Type: Host Rock
Age Young: Late Jurassic

Name: Slate
Role: Host
Age Type: Host Rock
Age Young: Late Jurassic

---

Analytical Data

Not available

---

Materials

Ore: Gold
Ore: Pyrite
Ore: Arsenopyrite
Gangue: Quartz
Gangue: Slate
Gangue: Schist

---

Comments

Comment (Economic Factors): Clark (1970) reported that the Wildman-Mahoney Mine produced approximately $5 million.

Comment (Geology): Ore Genesis Several mechanisms have been suggested as the source of the Mother Lode gold deposits. The most widespread belief is that plutonic activity magmatically differentiated vein constituents or provided the heat to circulate meteoric fluids or to metamorphose the country rocks to liberate the vein constituents. Knopf (1929) proposed that carbon dioxide, sulfur, arsenic, gold, and other constituents were emitted from a crystallizing magma but the components were carried by meteoric water in a circulation system driven by plutonic heat. Most theories suggest that gold deposits formed at temperatures of 300 to 350 degrees centigrade with a possible magmatic or metamorphic origin. Zimmerman (1983) proposed that the Mother Lode veins were generated by and localized near a major late Nevadan shear zone, the mechanism of ore genesis being the shearing and redistribution of mass within a major fault zone. He suggested that the early reverse faults had strike slip component, which is evident in the correlation of expected strike-slip dilatant zones with the geometries and steeply raking attitudes of the ore shoots. Fault movement and shearing would cause recrystallization of the rocks within the fault zone, releasing the more mobile elements including gold and most of the other vein constituents. Moreover, the heat generated by shearing would contribute to the metamorphism of the rocks in the fault zone and cause fluid circulation in the fault zone. Mineral laden auriferous fluids generated by this shearing channeled into the fault fracture system into dilatant zones, which represented avenues of increased flow and lower strain LOCAL GEOLOGY Metavolcanic and metasedimentary rocks of the Mariposa Formation host the gold-bearing veins in the Wildman-Mahoney Mine. These rocks make up a northwesterly striking, nearly vertical dipping sequence about 1 mile wide consisting of black, thinly laminated carbonaceous clay slate with occasional layers of fine-grained greywacke and interbedded units of greenstone which is locally altered to amphibolite schist. The principal gold bearing quartz veins are all localized within the steeply dipping foliated shear zones in the greenstone and slate units. Veins are not conformable with the foliation but cut across the foliation at a slight angle. The tabular veins have a sinuous northwestererly strike. The quartz veins in the Wildman-Mahoney (and adjoining Lincoln Mine) were all part of a single vein system that was up to 160 feet thick. The principal vein, was almost wholly contained in Mariposa slate and some associated amphibolite schist to the south in the Wildman claim, but branched northward into slate and greenstone country rock in the Mahoney claim and Lincoln Mine.

Comment (Development): Most of the important lode gold deposits in Amador County Mother lode were discovered in the 1850s while rich Tertiary placer deposits were being worked. The Wildman Mine, comprising the Wildman claim, was founded in 1851. The neighboring Mahoney Mine, comprising the Mahoney and South Mahoney claims, commenced operations in 1852. Both mines were worked intermittently from 1852 to 1924. By 1867, the Wildman Mine had a shaft 530 feet deep and a 12 stamp mill. From 1867 to 1887, the Wildman Mine lay idle before it was reopened by the Wildman Gold Mining Company (Logan, 1927). The Mahoney mine had been opened to a depth of 500 feet by 1873. The Mahoney worked a 45-foot wide vein that was profitable to 250 feet but below which carried only low-grade ore. The early day production from the Wildman to a depth of 500 feet, the Mahoney to a depth of 300 feet, and from the neighboring Stewart claim is estimated to have been about $1.5 million (Logan, 1927). The ore was worked in a shared 20 stamp mill. From 1887 to 1894, the Wildman Mine produced 94,2056 tons of ore which yielded $417,561 after deducting freight and smelting charges on the concentrates and bullion refining charges (Logan, 1927). In 1894, the Wildman Mining Company purchased the Mahoney Mine, and the mine became the Wildman-Mahoney Mine. At the time, the Mahoney shaft was 900 feet deep (Logan, 1927). The Wildman-Mahoney Mine was worked by the Wildman Gold Mining Company until 1906 when it was closed down. From 1894 to 1901, the Wildman produced 234,945 tons of ore of a total gross value of $834, 671, resulting in a net profit of over $200,000. During the same period, the Mahoney property produced 269,681 tons, which yielded a gross output of $518,037, but experienced an overeating loss of over $100,000. Total average cost of mining and milling, including development and other improvements except enlarging the mill averaged 2.59/ton during this period. In 1906, the Wildman-Mahoney Mine was acquired by the neighboring Lincoln Mine and incorporated into the Lincoln Consolidated Mines, the combined operations comprising 383 acres, with 4200 feet on the vein (Tucker, 1914). The Lincoln Mine shaft was deepened to 2000 feet, a drift was run south over 2200 feet passing through the Mahoney claim and to a point below the 1400-foot Wildman shaft. Long crosscuts were run into the footwall from the 500, 1200, and 1950 foot levels of the Lincoln Shaft, and on the 1200 foot level one was run into the hanging wall, all apparently without finding ore (Logan, 1927). The Wildman-Mahoney was reopened in 1908 and worked until 1912, after which it was permanently idled (Carlson & Clark, 1954). By then, the Wildman shaft had reached a depth of 1400 feet on a 72? incline, the Mahoney shaft 1200 feet deep on a 62? incline, and the Emerson shaft a vertical depth of 616 feet. The Wildman vein had been stoped to about 1400 feet and the Mahoney vein to 1200 feet deep (Logan, 1927). There is no record of the output between 1908 and 1911, but it is believed to have been small. By the time the Lincoln Consolidated Mines were permanently idled in 1912, the combined production of the Wildman-Mahoney properties was about $5.0 million (Clark, 1970).

Comment (Identification): The Wildman-Mahoney Mine is located immediately north of the town of Sutter C reek in the famous Mother Lode Gold Belt in the Sierra Nevada foothills of western Amador County. While the mine is technically in the smaller Sutter Creek district, the uniform nature of gold mineralization with neighboring districts has caused some authors to include the district into the Jackson - Plymouth district (Clark, 1970) which in sum was the most productive district of the Mother Lode belt with an estimated total production of about $180 million (Clark, 1970). The Wildman Mine (founded in 1851), and neighboring Mahoney Mine (founded in 1852), operated as independent mines until 1894, when they were merged into the Wildman-Mahoney Mine. In 1906, the Wildman-Mahoney Mine was acquired by another neighboring mine (Lincoln Mine) after which all three mines were operated as the Lincoln Consolidated Mines. The Wildman-Mahoney properties were operated until the Lincoln Consolidated mines ceased operation in 1912. By that time, Wildman Shaft was 1400 feet deep on a 72? incline and the Mahoney Shaft was 1200 feet deep on a 62? incline. Clark (1970), credited the Wildman-Mahoney Mine with a total production of $5 million.

Comment (Location): The location selected for latitude and longitude is the Wildman-Mahoney Mine symbol as illustrated on Fig. 4 of Zimmerman (1983). The mine is not shown on the USGS 7.5 minute Amador City quadrangle)

Comment (Geology): Mineralization is characterized by steeply dipping massive gold-bearing tabular quartz veins striking north to northwest and dipping between 50 to 80? east. Veins are discontinuous along both strike and dip, with maximum observed unbroken dimensions of 6,500 feet in either direction (Zimmerman, 1983), but individual veins more commonly range from structures 3,000 feet long and 10 to 50 feet wide to tiny veinlets. In rare instances, veins are known to reach as much as 200 feet thick (Keystone Vein). Veins may be parallel, linked, convergent, or en echelon, and commonly pinch and swell. Few can be traced more than a few thousand feet. At their terminations, veins pass into stringer zones composed of numerous thin quartz veinlets or into gouge filled fissures (Knopf, 1929). Ores consist of hydrothermally deposited minerals and altered wall-rock inclusions. Gold occurs as free gold in quartz and as auriferous pyrite and arsenopyrite. Quartz is the dominant mineral component in the veins, comprising 80-90% or more with ankerite, arsenopyrite, pyrite, albite, calcite, dolomite, sericite, apatite, chlorite, sphalerite, galena, and chalcopyrite in lesser amounts of a few percent or less. Cumulative sulfides generally range 1% - 3% of the rock (Carlson and Clark, 1954; Zimmerman, 1983). Ore grade material is not evenly distributed throughout the veins, but was localized in ore shoots, which tend to occur at vein intersections, at intersections of veins and shear zones, or at points where the veins abruptly change strike or dip (Moore, 1968). Ore shoots generally display pipe-like geometries raking steeply in the veins at 60-90%. Horizontal dimensions of the ore shoots are commonly 200-500 feet, but pitch lengths were often much greater, and often nearly vertical. Pockets of high grade ore are relatively abundant. Single masses of gold containing over 2,000 ounces and single pockets containing more than 20,000 ounces have been found. Silver is subordinate. Gold fineness averages 800. While most of the Mother Lode ore shoots mined have been less than 300 feet in strike length, many have extended down dip for many thousands of feet. In the deeper mines, mining continued to almost 6,000 feet on the dip of the vein with no evidence of bottoming. Cessation of operations in the deep Kennedy (5912') and Argonaut (5570') mines was caused by increasing costs at the greater depths rather than an absence of ore. Milling ore was generally low to moderate in grade (1/7 to 1/3 ounce per ton). Alteration Wall rocks have invariably been hydrothermally altered, having been partially to completely converted to ankerite, sericite, quartz, pyrite, arsenopyrite, chlorite, and albite with traces of rutile and leucoxene (Knopf, 1929). The mineralization is usually adjacent to the veins in ground that has been fractured and contains small stringers and lenses of quartz.. Locally, greenstone bodies (altered volcanic rocks) adjacent to the quartz veins contain enough disseminated auriferous pyrite in large enough bodies to constitute what has been called "gray ore". Altered slate wallrock commonly contains pyrite, arsenopyrite, quartz, chlorite, and sericite with or without ankerite (Zimmerman, 1983). Large bodies of mineralized schist also form low-grade ore bodies throughout the Mother Lode. This ore consists of amphibolite schist which has been subjected to the same processes of alteration, replacement, and deposition that formed the greenstone gray ores. The altered schist consists mainly of ankerite, sericite, chlorite, quartz, and albite. Gold is associated with the pyrite and other sulfides that are present. Pyrite comprises about 8 percent of the rock. The average grade of mineralized schist is about 0.1 oz per ton (Moore, 1968).

Comment (Commodity): Commodity Info: Free milling ores averaged $3.62 per ton.

Comment (Commodity): Ore Materials: Free milling gold in quartz with 2%-2 1/2% auriferous sulfides, primarily pyrite and arsenopyrite. Low grade gray ore consisting of hydrothermally altered greenstone and amphibolite schist mineralized with disseminated auriferous pyrite and arsenopyrite.

Comment (Commodity): Gangue Materials: Quartz, slate, schist

Comment (Geology): In the Wildman claim, at the south end of the Wildman-Mahoney, three separate ore bodies were worked; the main Wildman vein, the Granite Boulder lead, and the Magpie lead. The Wildman vein consists of a well-defined fracture-filling contact vein of solid quartz generally striking N 25?W and dipping 65?E. The vein varied markedly in width. At the surface it was 45 feet wide and produced much rich ore in early workings. On the 1400-foot level it averaged only 5 feet wide. On another level, the vein increased from less than 10 feet to 25 feet wide within 185 feet of the shaft, then pinched to as little as 10 feet before widening again to 100 feet within 666 feet from the shaft. The main Wildman pay shoot was 700 feet long with ore averaging $3.62 per ton. The Granite Boulder lead occurred on the foot wall or western side of the Wildman vein, between the Wildman vein and unmineralized foot wall slate. It consisted of a body of amphibolite schist traversed in all directions by auriferous pyrite bearing quartz stringers. The Magpie lead was similar in character to the Granite Boulder lead but occurred in black slate on the hanging wall side of the Wildman vein. The ore in the Granite Boulder and Magpie ore bodies was low grade (Tucker, 1914). At the north end of the Wildman claim, the Wildman vein branches (Brown, 1890) at a greenstone dike, both branches continuing into the Mahoney claim. At the junction, the vein has a width varying from 4 - 35 feet. The gouge is 12 feet thick on the hanging wall (Brown, 1890). The western branch comprises the principal Mahoney Mine contact vein and strikes N 20?W and dips 62?E. Ore in the Mahoney vein consisted of contact vein stringer leads within black Mariposa slate with a footwall of amphibolite schist (Tucker, 1914). The main Mahoney ore shoot was 1000 feet long and averaged 25 feet wide. Approximately one mile north of the Mahoney shaft, the Mahoney vein branched again, the split at an intervening an intervening greenstone body. One branch turned eastward with a greenstone foot wall. The larger western branch into the Lincoln Mine with schist, and farther off, greenstone on the hanging wall (Tucker, 1914, Logan, 1927). There was usually a heavy gouge with ore on both sides of this branch. In the upper levels, of the Mahoney-Wildman, most of the ore was in the Wildman and Mahoney contact veins along the schist or slate wall rock contact. Ore consisted of free milling quartz with about 2% pyrite and arsenopyrite with lesser amounts of chalcopyrite, galena, and sphalerite. Gold also filled fractures in the coarse sulfide grains. The highest-grade quartz veins usually showed black banded or ribboned quartz structures parallel to the vein walls. Free gold was present in the ribboned structures which were composed of parallel layers of quartz, crushed slate, pyrite, arsenopyrite, chlorite, and sericite (Hazlitt and Russell, 1990). Vein splits or intersections localize the higher-grade ore shoots and also result in areas of greater width and tonnage. Higher-grade ore zones are also found where the boundaries between rock units are cut by the vein structures. At depths of about 500 feet in the Wildman and 250 feet in the Mahoney, the mineralization began to pass from the contact vein into foot wall schist of the large low-grade Granite Boulder lead ore body. This gray ore body was from 60 to 295 feet thick. Mining continued to the 1300 foot level in the period between 1895 and 1899, the ore coming from the low grade ore between 500 and 1300 feet. Wall rock alteration is pervasive. Locally, the shear zones have been carbonate altered to a mixture of ankerite and sericite. Usually the higher-grade portions of the veins have intensely carbonate-altered gouge which are cut by narrow quartz veinlets impregnated with arsenopyrite and pyrite.

Comment (Workings): The following workings were reported for the Wildman-Mahoney Mine by the California Mining Bureau on August 19, 1914. Wildman Mine workings Wildman shaft - 1400 feet at 72? incline Emerson shaft - 619' vertical (located 900' E of Wildman shaft) 400 foot level - 720? S crosscut E 50' on north side of shaft, drift N 200' 500 foot level - crosscut W 60' to vein on north side of shaft, with drift S 400' and drift N 180'. 600 foot level - crosscut W 80' to vein, drift N 180' 700 foot level - crosscut W 40', drift S 680'- 80' on N side of shaft on 700' level, crosscut W 140' and crosscut E 640' 800 foot level - N 240', S 80' 900 foot level- 840'N, 140' S 1,000 foot level - 240'N, 140' S 1,100 foot level - 300' N, 160' S 1,200 foot level - 340' N, 280' S 1,300 foot level - 260' N, 500' S Mahoney Mine workings Mahoney shaft - 1200 feet at 62? incline (located 960' NW of Wildman shaft) 200 foot level - 240' N, 420' S 300 foot level - 180' N, 425' S 600 foot level - 260' N, 260' S 800 foot level - ---- , 550' S 900 foot level - 120' N, 820' S 1,000 foot level - ---- , 720' S 1,200 foot level 80' N, 100' S Mahoney workings are connected with the Wildman workings on the 600', 800', 900', and 1000' levels. Workings in slate were difficult to maintain and required heavy timbering or other ground support. To accommodate this, large stations were cut and additional sets were placed outside the main station sets with open lagging spaced 8 - 10 inches apart. Under pressure from ground swelling the light lagging would bend and eventually break, giving sufficient warning before significant damage to the main members of the set (Storm, 1900). The usual stoping method in slates was square set with almost immediate backfilling. Gray ore and amphibolite schist were much more competent, and haulage ways and development openings in unfractured ground were untimbered. Various mining methods were used in these ores of the Mother Lode including square set, shrinkage, open-stoping with random pillars, block caving and glory hole (Moore, 1968).

Comment (Deposit): The Wildman-Mahoney Mine produced from typical Mother Lode type low sulfide mesothermal gold quartz veins. The principle veins are part of a single NNW-SSE striking, steeply dipping vein system that extends northward through the Wildman, Mahoney, and neighboring Lincoln Mine. The Wildman Vein strikes N 25?W. The main Mahoney Vein strikes N 20?W and dips 62?E. The Wildman Vein strikes N 25?W. Vein ore consisted of free gold and auriferous pyrite and arsenopyrite within pipe-like steeply raking ore shoots. Ores shoots were typically richer at vein intersections and at lithologic contacts. Gold values were typically low to moderate in grade, averaging 1/7 to 1/3 ounces of gold per ton. Secondary, low grade, ores also occurred as hydrothermally altered slate, greenstone, and amphibolite schist wallrock containing disseminated auriferous pyrite ('gray ore").

Comment (Geology): REGIONAL GEOLOGY The Wildman-Mahoney Mine is located within the Sierra Nevada foothills, where bedrock consists of north trending tectonostratigraphic belts of metamorphosed sedimentary, volcanic, and intrusive rocks that range in age from late Paleozoic to Mesozoic. Locally, the Mesozoic rocks are capped by erosional remnants of Eocene auriferous gravels and once extensive volcanic rocks of Tertiary age. The structural belts, which extend about 235 miles along the western side of the Sierra, are flanked to the east by the Sierra Nevada Batholith and to the west by sedimentary rocks of the Cretaceous and Jurassic Great Valley sequence. In Amador County, the structural belts are internally bounded by the Melones and Bear Mountains fault zones. Schweickert and others (1999) provide one interpretive overview of the regional geology of this part of the Sierra Nevada. Gold deposits in the Plymouth - Jackson district occur within the north and northwest trending mile-wide Mother Lode Belt, which is dominated by gray to black slate of the Upper Jurassic Mariposa Formation and associated greenstone and amphibolite schist bodies assigned to its Brower Creek Volcanics member. In Amador County, the Mother Lode Belt approximately parallels Highway 49 southeastward from Plymouth through the town of Jackson. The geology of this segment has been mapped by Zimmerman (1983) and Duffield and Sharp (1975). The lode gold deposits along this stretch are responsible for most of the gold production in the county, which has been reported to be 7.68 million ounces (Koschman and Bergendahl, 1968). Clark (1970) placed the value of this production at $180 million. The Amador County portion of the belt was one of the most productive gold mining areas in the United States, and the Plymouth - Jackson district in Amador County was the most productive part of the belt. The Mariposa Formation contains a distal turbidite, hemipelagic sequence of black slate, amphibolite, schist, and fine-grained tuffaceous rocks, and volcanic intrusive rocks. The thickness of the Mariposa Formation is difficult to ascertain due to structural complexities, but is estimated to be about 2,600 feet thick at the Cosumnes River. Massive greenstone of the Upper Jurassic Logtown Ridge Formation lies west of the Mother Lode Belt. The contact between the Logtown Ridge and Mariposa Formation is generally gradational (Zimmerman, 1983). The Logtown Ridge Formation consists of over 9,000 feet of volcanic and volcanic-sedimentary rocks of island arc affinity. These rocks are mostly basaltic and include flows, breccias, and a variety of layered pyroclastic rocks. Metasedimentary rocks, chiefly graphitic schist, metachert, and amphibolite schist of the Calaveras Complex (Carboniferous to Triassic) are to the east. Mother Lode Gold Quartz Veins Mother Lode-type veins fill voids created within faults and fracture zones. The Mother Lode Belt consists of a vein system ranging from a few hundred feet to a mile or more in width. The vein system consists of a fault zone containing several parallel veins separated by hundreds of feet of highly altered country rock containing small quartz veins and occasional bodies of low-grade ore. Veins are generally enclosed within numerous discontinuous fault fissures within Mariposa Formation slate, associated greenstone, amphibolite schist, or along lithologic contacts. Mineralized fault gouge is abundant.

---

References

Reference (Deposit): Duffield, W.A. and Sharp, R.V., 1975, Geology of the Sierra foothills melange and adjacent areas, Amador County, California: U.S. Geological Survey Professional Paper 827, 30 p.

Reference (Deposit): Logan, C.A., 1927, Amador County, Lincoln Consolidated Mines: California State Mining Bureau, 23nd Report of the State Mineralogist, p. 170-172.

Reference (Deposit): Zimmerman, J.E., 1983, The Geology and structural evolution of a portion of the Mother Lode Belt, Amador County, California: unpublished M.S. thesis, University of Arizona, 138 p.

Reference (Deposit): Logan, C.A., 1934, Mother Lode gold belt of California: California Division of Mines Bulletin 108.

Reference (Deposit): Moore, L., 1968, Gold resources of the Mother Lode Belt, El Dorado, Amador, Calaveras, Tuolumne, and Mariposa counties, California: U.S. Bureau of Mines Technical Progress Report 5, p. 1-22.

Reference (Deposit): Schweickert, R.A., Hanson, R.E., and Girty, G.H., 1999, Accretionary tectonics of the Western Sierra Nevada Metamorphic Belt in Wagner, D.L. and Graham, S.A., editors, Geologic field trips in northern California: California Division of Mines and Geology Special Publication 119, p. 33-79.

Reference (Deposit): Tucker, W.B., 1914, Amador County, Lincoln Consolidated Mines: California State Mining Bureau, 14th Annual Report of the State Mineralogist, p. 36.

Reference (Deposit): Koschman, A.H., and Bergendahl, M.H., 1968, Principal gold-producing districts of the United State: U.S. Geol. Survey Prof. Paper 610, 53 p.

Reference (Deposit): Clark, W. B., 1970, Gold districts of California: California Divisions of Mines and Geology Bulletin 193, p. 69-76.

Reference (Deposit): Carlson, D.W., and Clark, W.H., 1954, Mines and mineral resources of Amador County, California: California Division of Mines and Geology, 50th Report of the State Mineralogist, p. 185-196.

---

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.