Argonaut Mine (Pioneer Mine; Sunset), Martell, Jackson-Plymouth District, Mother Lode Belt, Amador Co., California, USA
|Latitude & Longitude (WGS84):||38° 21' 47'' North , 120° 47' 7'' West|
|Latitude & Longitude (decimal):||38.36306,-120.78528|
|Köppen climate type:||Csa : Hot-summer Mediterranean climate|
A former Au mine located in secs. 17, 20 & 21, T6N, R11E, MDM, 1.0 km (0.6 mile) ESE of Martell and about 1½ miles NNW of Jackson, on the California "Mother Lode," on private land. Discovered in 1850. Closed March, 1942. Owned by the Argonaut Mining Co., Ltd. of San Francisco. Operated by B. Monte Verda and E. C. Taylor. MRDS database stated accuracy for this location is 100 meters.
The Argonaut Mine is located one mile northwest of the town of Jackson, California, in the famous Mother Lode Gold Belt in the Sierra Nevada foothills of western Amador County. The Jackson-Plymouth district was the most productive district of the Mother Lode belt, with an estimated total production of about $180 million (Clark, 1970). The Argonaut Mine alone produced $25.2 million (Clark, 1970).
While discovered in 1850, the Argonaut Mine lay largely undeveloped until purchased by the Argonaut Mining Company in 1893, after which the mine remained in continuous operation until 1942 except for a period of 3 years when mining was discontinued due to the results of mine fires (Vanderburg, 1930). From the 1890s until 1942, the Argonaut Mine and its neighbors become one of the most important gold mining districts in the nation, with the district producing $2 million - $4 million annually. The Argonaut Mine, itself became one of the deepest gold mines in the nation, bottoming at a vertical depth of 5570 feet.
Most of the important lode gold deposits in Amador County were discovered in the 1850's while rich Tertiary placer deposits were being worked. During this period, a 20-mile long belt of gold mineralization, part of the famous Mother Lode, was identified running through western Amador County, and the towns of Jackson, Sutter Creek, Amador City, and Plymouth flourished to support the new mines. While many of the local mines had been discovered and several had become large and profitable mines by 1875, several of the more important mines, including the Argonaut, Kennedy, Central Eureka, Bunker Hill, Fremont-Gover, and Lincoln Consolidated Mines did not become important producers until the 1880s and 1890s.
The Argonaut property was first opened in 1850 after discovery by two black miners named James Hager and William Tudor. From 1850 to 1893 it was worked in a primitive manner under the name of the Pioneer Mine. During this time exploration was confined to surface trenching and the driving of an adit on the north end of the Pioneer claim to cut the vein at a depth of several hundred feet (Vanderburg, 1930). Meanwhile, the neighboring Kennedy Mine was being actively worked while the Pioneer lay undeveloped. The Pioneer Mine is said to have been offered to the Kennedy Mine owners several times for $30,000, but they declined (Logan, 1927). By 1876, the mine had reached only 150 feet along the 18-foot wide Pioneer ore-shoot (Logan, 1934).
In 1893, the mine was purchased by the Argonaut Mining Company and renamed the Argonaut Mine. The Argonaut claims covered 4800 feet along strike of the Mother Lode. The Argonaut Company explored the deeper portions of the ore body by sinking and inclined shaft in the hanging wall of the vein with crosscuts and drifts driven from the main shaft. Shallow ores were rich and highly profitable. The ores were crushed in a 40 stamp mill. Details of early milling operations are provided by Storms (1900). Due to the heavy ground encountered, exploratory work could not be carried very far in advance of actual mining operations, as the maintenance expense entailed in keeping the workings open would have been prohibitive (Vanderburg, 1930).
There were two noted lawsuits between the Argonaut and adjoining Kennedy Mine in 1894 and 1897. In both cases, the Argonaut Mining Company accused the Kennedy Mine of conducting mining operations on their claims. In 1894, at a depth of 1200 feet, a vein branched from the main Argonaut vein into the hanging wall. The Kennedy Mine contended that this was an older vein, which had been displaced about 700 feet by normal faulting as measured along the Argonaut fissure. Ultimately, the courts ruled in favor of the Argonaut (Clark, 1952a). When the shaft reached 1750 feet in 1897, another dispute arose with the Argonaut again alleging the Kennedy was encroaching on their ground (Logan, 1927). To prove their case, the Argonaut owners were forced to prove their vein continued through to the apex of their ground. Since the shaft was not on the vein, raises had to be driven the entire distance to delineate the vein. Having proved the apex on their ground, they were awarded heavy damages against the Kennedy (Logan, 1927).
Between 1914-1919, the Argonaut was worked between the 3400 and 4800-foot levels and produced the best average grade of ore of any mine along the Mother Lode, averaging $10 - $13 per ton (Logan (1934). Between the 4500 - 4800-foot levels the ore averaged about $14.50 per ton.
Mining was halted in 1919, when a severe underground fire broke out on the 4000-foot level. At this time the mine had reached an inclined depth of 4800 feet. Within a short time, the fire was thought to be under control and work was resumed. But in early March, 1920, fire was discovered on the 3300-foot level of the adjoining Kennedy Mine, having presumably burned its way through old workings and caved ground. On March 17, 1920, the Kennedy management began filling the mine with water, and as the two mines were connected, the lower levels of both were flooded. Water rose to within 50 feet of the 3150 level of the Argonaut. Dewatering of the Argonaut began that summer, but they found the job too much for their plant alone and the Kennedy joined in the work which was completed in April, 1921. The fire caused the loss of a year's production. By the end of 1921, operations were back in full swing. On August 22, 1922, however, fire was again discovered on the 3350-foot level in the main shaft. A shift of 47 men working on the 4650 and 4800-foot levels was trapped, and before they could be rescued, the shaft was on fire and all were lost. For 22 days, rescuers tried reach the miners from a neighboring mine tunnel. Their efforts were in vain. A detailed account of the tragedy is captured in the book 47 Down: the 1922 Argonaut Gold Mine Disaster (Mace, 2004). This fire closed the mine for another year.
The mine was not cleared and ready for operation until July, 1923 after which it remained in steady operation until 1942. Between 1910 and 1934, the tonnage of ore handled annually ranged from 62,000 to 91,000 tons. By 1930, the Argonaut Mine had produced $16,377,252 (792, 250 ounces of gold), and was producing 260 tons of ore per day (Vanderburg, 1930).
The Argonaut Mill used 60 stamps, amalgamation, classifiers, and vanners. Al concentrates were chlorinated until the advent of cyanidation in 1896 and the construction of smelters in the San Francisco area in 1901 (Moore, 1968) From 84 - 91 percent of the gold was recovered from the ore containing about 1/3 ounce of gold per ton. In 1936, ball mills and flotation cells were installed making it possible to raise recovery to 94 % (Clark, 1952a). Details of the Argonaut milling operation during the 1930s are provided by Logan (1934).
The tailings were sold to a custom cyanide mill for further treatment (Moore, 1968). Between 1923 and 1938, the Amador Metals Reduction Company treated the Argonaut mine tailings. During this period, about 70,000 tons of tailings were treated resulting in a recovery averaging $60,000 per year (Clark, 1952b). Processing involved hydraulicking the tailings into a classifier and cyaniding. Because of the carbonaceous nature of the ore, sands and slimes were pre-coated with coal tar to prevent precipitation of the dissolved gold in the cyanide solution. The sands were then treated in leaching vats while the slimes were directed to an agitator and filtered on Oliver filters. Sand and slime residues were discharged. The solution was then precipitated, roasted, and the gold melted into bullion (Clark, 1952b).
The Argonaut Mine was closed in 1942 under Government Order L-208 (Gold Mine Closing Order) to help the war effort. The upper part of the mine was kept dewatered and in repair in hopes of eventual reopening. Due to escalating costs and the government imposed fixed gold price, the mine never reopened and the Argonaut Mining Company was dissolved in 1948.
Through December 31, 1942, production was 2,750,000 tons of ore from which $25,179,160.43 was recovered. The Argonaut Mining Company paid shareholders dividends of $3,789,750 on their original capitalization of $1 million (Clark, 1952a).
After closure, the surface plant and other surface facilities were sold.
Mineralization is a quartz 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 slate, greenstone & schist. The ore body is tabular and pinch and swell in form, strikes N10W and dips 40-60NE at a thickness of 3.66 meters. The quartz vein dips 40 NE in the upper workings, cutting across greenstone and slate. Branching and orientation of the vein was probably due to fault complications. About 500 feet from surface the vein is concordant with slate bedding and lies along the contact of slate with schist. The contact dips 64NE. The vein is fairly regular and continuous, varying in thickness from 8 to 12 feet. Free-milling ribboned structures of quartz, crushed slate, free gold, and sulfides that occurred within a few feet of the foot wall. Controls for ore emplacement included ore shoots within mesothermal gold-bearing quartz veins.
Auriferous sulfides, primarily pyrite, and to a lesser extent galena and arsenopyrite, comprised about 2% to 2½% of the ore. Gangue materials include quartz, slate, greenstone, amphibolite schist, pyrrhotite, chalcopyrite, and tetrahedrite. Local rocks include Mesozoic volcanic rocks, unit 2 (Western Sierra Foothills and Western Klamath Mountains).
Regional geologic structures include the Bear Mountains fault zone and the Melones fault zone. Local structures include the Melones fault zone.
The Argonaut Mine developed the Argonaut or Pioneer vein, a mesothermal gold-quartz vein occupying the fissure of a reverse fault that cut through beds of greenstone, schist, and slate. The vein was noteworthy for its continuity, having been followed from the apex down to the 5,400-foot level without a significant break. The quartz filling pinches and swells along both the strike and dip, but never dies out entirely (Vanderburg, 1930). The general strike of the Argonaut vein varies from N 10? - 18? W. At the 290-foot level, the vein dips 40? northeast, from the 470 level to the 4050-foot level it dips at 64?, and below the 4050- foot level the dip varies from 60? - 63? (Clark, 1952a). The vein ranges from 8 - 10 feet wide in the upper workings and thickens with depth. On the 3700-foot level, the Argonaut fissure is 7-10 feet wide and half filled with gouge and half with quartz. On the 4200-foot level it is 20 feet wide, increasing to 30 feet wide on the 4350-foot level. On the 4800-foot level, it widened rapidly to as much as 60 feet before narrowing considerably on the 4950 and 5100-foot levels where the ore shoot shortened, became flatter, and of lower grade (Logan, 1934). Essentially, all ore was contained in the single large vein, but there were numerous splits from the main vein into the hanging wall and foot wall (Zimmerman, 1983).
The Argonaut vein is enclosed within greenstone wall rock to a depth of 290 feet. Near the vein, the greenstone has been altered to amphibolite schist (Logan, 1934). From 290 feet to the 470-foot level, the vein traverses a narrow belt of Mariposa slate. The hanging wall side of the slate has been thrust up 125 feet along the fault. To a depth of 2500 feet the vein is on or near the contact between a slate foot wall and schistose greenstone hanging wall contact (Clark, 1952a). From there downward, the foot wall country rock is hard gray schist, but with a casing of Mariposa slate between it and the vein, and the hanging wall is Mariposa slate (Logan, 1934). Sills of greenstone, now standing near vertically and entirely altered to schist, occur within the Mariposa slate, and as a result, on certain levels, the immediate hanging wall is greenstone and the foot wall is slate. The vein is usually accompanied on one or both walls by gouge which varies from several inches to several feet thick.
The main quartz ore body in the Argonaut Mine was locally over 1000 feet long horizontally and about 5000 feet long vertically, but included barren or low-grade zones (Logan, 1934). Individual ore shoots ranged from 1 foot to 60 feet wide with an average of about 6-12 feet (Knopf, 1929). The main ore shoot which had been the mainstay of the Argonaut and Kennedy mines did not appear until about 1400 feet downdip from the surface where the upper portion of the veins fissure system intersected a slate-greenstone contact (Zimmerman, 1983). Between the 3600 and 4200-foot levels, because of its north pitch, the ore shoot was in the adjoining Kennedy Mine, then returned to the Argonaut (Logan, 1934). Around the 4800-foot level, the ore shoot was a lens of quartz about 950 feet long and 25-60 feet wide, raking southward about 50? between the vein and the hanging wall, and tapering gradually at each end. On the foot wall side there was a thick zone of post mineralization fault gouge made up of crushed slate and quartz fragments. Ribboned quartz developed along the foot wall side of the vein and showing free gold and carrying appreciable quantities of pyrite with trace amounts of sphalerite, galena, and chalcopyrite provided the best ore (Hershey, 1927). The hanging wall part of the vein was typically very low grade or barren massive quartz with black inclusions of hanging wall slate and scattered pyrite. Between the 4950 and 5100-foot levels, the ore shoot shortened, became flatter, and of lower grade. Ore grade remained unusually poor to the 5500-foot level, where a junction of two veins yielded a large low-grade quartz body (Logan, 1934). On the 5700-foot level, the north drift showed ore from 6 - 17 feet wide extending 200 feet north to the Kennedy Mine property. In the south drift on this level, three ore shoots, 158 feet, 235 feet, and 170 feet long respectively, varied from 5 -12 feet wide and ranging from $3 -$12 per ton (Logan, 1934).
The maximum width and length of the largest ore shoot was 65 feet and 1100 feet respectively. The average width mined was about 20 feet (Vanderburg, 1930). This ore shoot split into two branches near the 5400-foot level, below which they were worked independently (Logan, 1934). Other ore shoots above the 4200 foot level reported by Tucker (1914) include one 325 feet long averaging 10 feet wide and another of 600 feet long and averaging 10 feet wide.
The best ore consisted of a ribboned structure of quartz, crushed slate, free gold, and sulfides that occurred within a few feet of the foot wall. Ore was free milling and most of the gold was recovered by crushing and amalgamation. The yearly average grade of ore varied from $6 to $17 per ton. Sulfides comprised about 2- 2 1/2% of the ore. The amount of sulfides was not indicative of the richness of the ore (Vanderburg, 1930). On average, the concentrate contained about 16% of the gold recovered and ran up to about $100 per ton for the highest grade ore (Logan, 1927). Ore from the 5500 and 5700-foot levels averaged as much as 2.5 % concentrate which contained 2.6-5.0 ounces of gold per ton, and from which yielded 22% of the gold and 38% of the silver recovered. Pyrite was the most abundant sulfide, with galena and arsenopyrite also yielding gold. Pyrrhotite, chalcopyrite, and tetrahedrite occurred sparingly (Logan, 1934).
In addition to the pre-mineral fault fissure, post-mineralization faulting was important in modifying the geometries of the Argonaut vein and its contained ore shoots. There are important oblique faults and smaller post-mineral faults within the vein. Three primary post-mineral faults were recognized in the mine. The "No.1 fault" has a horizontal throw of at most 80 feet on the 2880 foot and 3000 foot levels and persisted with depth. The No. 2 fault, south of the No.1, has a horizontal throw of 50 feet on the 5700-foot level. The No. 3 fault (200 feet south of the No.2), also has a 50-foot throw. On the south side of the workings, the ore is thought to be bounded by another oblique northwest striking fault, its trace on the plane of the vein dipping 70?-75? northeast. In several places where the fault cut the vein, a thick section of barren or poorly mineralized quartz comprised the hanging wall, while only a few feet of ribboned quartz ore occurred on the foot wall side (Logan, 1934).
Workings include underground openings with an overall depth of 1,295.4 meters. A 3-compartment shaft was sunk at a 60 degree incline to 4,250 feet. From surface to the 290 foot level, the shaft is completely in greenstone. From the 290 level to the 1,570 foot level it is in slate. From 1,570 foot level to the 2,520 foot level it is in schist, and below the 2,520 foot level it is in slate. Workings went to the 6,300 foot level with a 5,570 foot vertical shaft. Underground development comprised some 8 miles of drifts and cross-cuts plus more than 50 miles of excavated stope floors.
The Argonaut Mine was worked through a 5,800-foot 70 degree inclined shaft sunk in the hanging wall of the vein. An auxiliary shaft was also maintained for ventilation and as an escape route. The three-compartment shaft was divided into one man and two hoisting compartments, each of dimensions 5 feet 9 inches x 4 feet 1 inches. The greater portion of the shaft was timbered with 20 inch x 20 inch fir sets, but later operations employed 16 inch by 16 inch wall plates 16 feet long, 14 inch by 16 inch end plates 6 feet long, 10 inch by 16 inch dividers 6 feet long, and 8 inch by 12 inch posts 3 feet p inches long. The sets were placed on 5-foot centers. Lagging was 2 by 6 or 3 by 6 inch. Drifts and crosscuts were also heavily timbered to combat swelling ground. Details of timbering in drifts, crosscuts and raises are given by Vanderburg (1930).
Shaft levels were driven at the 290', 380', 470', 560', 740', 830', 920", 1010', 1130', 1240', 1350', 1460', 1570', 1690', 1800,'1920', 2040', 2160', 2280', 2400', 2520', 2640', 2760', 2880', 3000', 3150', 3300', 3450', 3600', 3750', 3900', 4050', 4200', 4350', 4500', 4650', 4800', 4950', 5100', 5250' 5400,' 5500', 5800', 6000', 6150', and 6300' ("'" = feet).
The lower levels were accessed through a winze sunk from the 5500 foot level, 300 feet south of the shaft. The deepest 6300-foot level was 5570 vertical feet below the collar of the shaft (Clark, 1952a). Levels were turned from the winze at 5700, 5800, 6000, 6150, and 6300 feet.
There are approximately 8 miles of drifts, crosscuts, and tunnels, 4 miles of raises, and 50 miles of stope floors (Clark, 1952a). The mine had several connections to the Kennedy Mine (Vanderburg, 1930 figure). A connection to the adjoining Kennedy Mine was maintained at the 4650 level.
Vanderburg (1930) provides a plan of the lower mine levels and a vertical projection of the Argonaut shaft.
Development consisted of driving a crosscut from the main shaft to the vein. From the crosscut drifts were extended along the foot wall. Crosscuts and drifts, 6 feet by 8 feet in cross section, were timbered with regular drift sets. After a drift was driven several hundred feet, a raise was driven to connect with the level above top provide an additional escape route and to aid air circulation on the level (Vanderburg, 1930).
The method of stoping used at the Argonaut Mine was an adaptation of the square-set system followed closely by waste filling. Since the ore body and its walls had insufficient strength to remain open, as stoping progressed, temporary timber support was required, followed promptly by waste filling (Vanderburg, 1930). Stoping was carried out in sections about 100 feet long, or as long as the distance between two consecutive manways. Several sections were usually mined at the same time. Practically all the vein material in the ore shoot was mined without sorting. No pillars were left. Additional details of stoping and methods are provided by Vandenburg (1930).
All ore and rock was trammed underground in 1-ton end dump cars. Mechanical haulage was not used since the distance from the shaft to the ore body was small.
Before 1936, milling was done in a 60-stamp mill. After stamping, the pulp was concentrated, classified, and the tailings were cyanided. In 1936, ball mills and flotation cells were installed making it possible to raise recovery to 94 % (Clark, 1952a).
Production data are found in: Logan, Clarence August (1927).
Production comprised 2,750,600 dry tons of ore yielding $25,179,160.43 in Au at $35.00 U.S. per Troy Ounce (722,262 Troy Ounces). The yearly average grade of ore varied from $6 to $17 per ton. Dividends paid totaled $3,789,750 on an original capitalization of $1 million (Clark, 1952a).
Production figures reported by Joralman (1941) for the Argonaut Mine show a grade of 0.5 ounce per ton from 1897 to 1925, and 0.31 ounce /ton from 1926 to 1940, with an overall average grade of 0.406 ounce/ton (Zimmerman (1968).
Assay data results: Concentrates assayed up to $100 per ton.
10 valid minerals.
This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.
Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org
|Late Jurassic - Triassic|
145 - 252.17 Ma
|Jurassic marine rocks, unit 1 (Western Sierra Nevada and Western Klamath Mountains)|
Age: Mesozoic (145 - 252.17 Ma)
Stratigraphic Name: Agua Fria Formation; Colfax Formation; Cosumnes Formation; Galice Formation; Hunter Valley Cherts; Mariposa Formation; Merced Falls Slate; Salt Spring Slate; Jasper Point Formation
Comments: Western Klamath Mountains, western Sierra Nevada. Primarily slate and metamorphosed graywacke; minor siltstone, conglomerate, chert, and volcanic rocks. Mainly Late Jurassic in age, but also includes some Early Jurassic or older rocks
Reference: Horton, J.D., C.A. San Juan, and D.B. Stoeser. The State Geologic Map Compilation (SGMC) geodatabase of the conterminous United States. doi: 10.3133/ds1052. U.S. Geological Survey Data Series 1052. 
|Jurassic - Triassic|
145 - 252.17 Ma
|Mesozoic sedimentary and volcanic rocks|
Age: Mesozoic (145 - 252.17 Ma)
Reference: Chorlton, L.B. Generalized geology of the world: bedrock domains and major faults in GIS format: a small-scale world geology map with an extended geological attribute database. doi: 10.4095/223767. Geological Survey of Canada, Open File 5529.