Old Eureka Mine (Eureka Mine; Amador Consolidated Mine; Hetty Green Mine; Hayward Mine; Amador claim; Maxwell claim; Alpha claim; Railroad claim), Central Eureka Mine (Summit Mine), Sutter Creek, Jackson-Plymouth Mining District, Amador County, California, USAi

Regional Level Types
Old Eureka Mine (Eureka Mine; Amador Consolidated Mine; Hetty Green Mine; Hayward Mine; Amador claim; Maxwell claim; Alpha claim; Railroad claim)	Mine
Central Eureka Mine (Summit Mine)	Mine
Sutter Creek	Creek
Jackson-Plymouth Mining District	Mining District
Amador County	County
California	State
USA	Country

A former lode Au-Ag mine located in the E½E½ sec. 7 and in the W½W½ sec. 8, T6N, R11E, MDM, 0.6 km (0.4 mile) SSE of Sutter Creek (town) proper (within the town limits), on private land. The Old Eureka was discovered in 1852. Operated by the Central Eureka Mining Co. MRDS database stated accuracy for this location is 100 meters. This mine adjoins the Central Eureka Mine. Owners of the Central Eureka connected the two workings by an upper adit. Operated successfully until 1881, at which time it was 1,965 feet deep.

The Old Eureka Mine is located within the town of Sutter Creek in the famous Mother Lode Gold Belt of western Amador County. The Central Eureka Mine adjoins the Old Eureka to the south and the Wildman-Mahoney and Lincoln Consolidated Mine lie to the north. 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 consolidate the smaller neighboring districts into a single Jackson - Plymouth district (Clark, 1970). 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 Old Eureka Mine was first opened in 1852 and at various times during its history was known as the Hayward, Eureka, Hetty Green, Badger and Wolverine, and Amador Consolidated mines. The Old Eureka Mine was operated independently until 1924 when it merged with the Central Eureka Mine, the combined properties operating as the Central Eureka Mine. The combined Central Eureka Mine is credited with producing $36 million (Clark, 1970). The old Eureka properties are credited almost $28 million of that amount.

The Old Eureka Mine was first opened in 1852 and comprised the Amador, Maxwell, Alpha, and Railroad claims. This mine has also been known at times as the Hayward, Eureka, Hetty Green, Badger and Wolverine, and Amador Consolidated mines. In 1852, a 10 stamp mill was and by 1855, an initial whim shaft had been sunk to about 95 feet with a lower level driven about 144 feet (Trask, 1855) and a 100 foot adit entered the mine from the west. The initial ore shoot commenced at the surface and extended about fifty feet in depth and was highly pyritiferous. Another ore shoot encountered at the bottom of the shaft was much more productive with almost no pyrite, but instead containing a veinlet of metallic gold (not disseminated) at time exceeding 3/8 inch wide. The same vein had been struck in an adjoining Badger Mine 1000 feet to the south. This is the only instance of a true vein of metallic gold having been found in the state (Trask, 1855). A new 20 stamp mill was built on the Old Eureka in 1856 and 20 more stamps were added in 1857.

Alvinza Hayward acquired control of both the Old Eureka and Badger mines in 1859 and consolidated them under the Old Eureka Mine. The adjoining claim on the south was the Badger claim on which 10 stamps were built in 1854 (Logan, 1934). In 1857, the consolidated properties had a north shaft 1230 feet deep, a middle shaft 960 feet deep, and a southern shaft at 760 feet deep. By then there were 56 stamps operating in the two mills crushing 80 tons per day, and ore was also sent to custom mills (Logan, 1934). Hayward was very secretive and refused to divulge the details of his production, but local reports placed the output at $6 million up to 1867 (Logan, 1934). In 1866 it was said that 30,000 tons yielded $27 per ton at a working cost of $5 per ton. . In March 1869, the mine was purchased by the Amador Mining Company for $750,000. The Amador Mining Company operated the Old Eureka until 1881. For the year ending July 1, 1869, 30,361 tons of ore yielded $617,542 or $20.34 per ton. For 14 months ended April 1, 1875 the yield was $239,717 in bullion and $20,254 from concentrates, from 22,098 tons of ore indicating a decline in ore quality. In 1886, after the mine had attained a depth of about 2000 feet and had produced about $16,000,000, it was closed and remained idle for a period of 30 years during which time the mine was acquired by Hetty Green (at one time the country's richest woman). In 1916, a new company purchased the property for $500,000. The old shaft was in very bad shape having been sunk in Mariposa slate. About $200,000 was spent to reopen, dewater, and rehabilitate the shaft and on equipment and pumping. The shaft was deepened to 3500 feet (3212' vertical depth) and drifts were run north and south on the main fissure at 1700', 2100', 2950', and 3500 feet together with approximately 1500 feet of crosscuts (Norman, 1939). The 1200 foot level was also reopened On each of these, except the lowest, from 1450 feet to 1640 feet of drifts were run. A crosscut was run west 800 feet on the 3500 foot level. All of this exploration failed to reveal paying ore. Total drifts as of July 1, 1920 were 1720 feet on the 1700 foot level, 1345 feet on the 2125 foot level, and 1685 feet on the 2950 foot level. Crosscuts totaling about 1500 feet had been driven in the foot and hanging walls. Several new levels were driven without finding commercial ore in paying quantities. Work was discontinued in 1921.

In 1924, the Old Eureka was purchased by the Central Eureka Mining Company after threats of litigation over rights to the rich ore shoot being mined from the lower levels of the Central Eureka Mine on the south (Norman, 1939). Operations were merged with those of the Central Eureka Mine. From 1924 to 1930, when the lower levels of the Central Eureka were abandoned, the Central Eureka Mining Company confined its working to its principal ore body on the south line of the Old Eureka and to active exploration of the Old Eureka workings. After 1930, all of the ore produced from the Central Eureka Mine came from the Old Eureka properties.

In 1930, mining on the old abandoned 2100-foot level was started. While the previous operators had directed their efforts to the south side of the Old Eureka shaft and adjacent to the Central Eureka Mine, the Central Eureka Mining Company started drifting northward. On the 2000', 2100', and 2300 foot levels, drifts were run in part along small contact ore bodies and in part along a shear zone in the hanging wall greenstones. In the later part of 1936, after stoping of the new ore above the 2500-foot level, a different approach to its development and mining was implemented. The unsuccessful efforts to profitably mine the small ore bodies on the long upper levels, mainly from one level at a time, necessitated the opening of the new ore on several levels simultaneously. The old shaft was dewatered and cleaned out to the 3000-foot level, from where a drift was run northward 1800 feet and a raise to connect with a winze that had been started on the 2500-foot level. Sub-levels were then run to several advantageous levels. This program was successful and dividends of $108,000 and $240,000 were paid out in 1937 and 1938 respectively (Norman, 1939).

As were all gold mines in the district, the Central Eureka Mine was shut down in 1942 for WW II, but in anticipation of its reopening, it was kept in working order during the war. Mining was resumed in 1946 but little ore was produced until 1948. In 1951, 39,440 tons of ore yielded a little more than $500,000, but because of greatly increased costs, the Central Eureka was permanently shut down in the early 1950's. Various reports place its final year of operation as 1951 or 1953. It was the last active major gold mine on the Mother Lode with a total production of approximately $36 million (Carlson and Clark, 1954).

Mineralization is a 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 andesite, Late Jurassic greenstone and slate of the Mariposa Formation. The ore body(ies) is/are tabulatr/pinch & swell in form. There are 2 veins termed the "Boulder ledge" and the "True ledge" which were worked. The Boulder ledge was on the W at 15 to 20 feet thick, and yielding $10 per ton (period values), having the best grade ore between the 800 and 1,350 foot levels. The True ledge varied from 3 to 15 feet thick on the middle levels, and was of a much higher grade. The main vein had a slate footwall, heavy gouge, and a meta-andesite hanging wall. Ore materials included: free-milling banded quartz-slate seams and hydrothermally altered greenstone with disseminated auriferous sulfides, primarily pyrite and arsenopyrite. Gangue materials included: quartz, slate, ankerite, albite, sphalerite and greenstone. Controls for ore emplacement include ore shoots within mesothermal gold bearing quartz veins. Local alteration includes wall rocks hydrothermally altered, having been partially to completely converted to ankerite, sericite, quartz, pyrite, arsenopyrite, chlorite, and albite. Locally, greenstone bodies adjacent to the quartz veins contain enough disseminated auriferous pyrite in large enough bodies to constitute low-grade ore. Local rocks include Jurassic marine rocks, unit 1 (Western Sierra Nevada and Western Klamath Mountains) and/or Mesozoic volcanic rocks, unit 2 (Western Sierra Foothills and Western Klamath Mountains).

The Wolverine fault is the most prominent structural feature in the Old Eureka Mine. The fault strikes N 20? W and dips 65? east and displays measurable displacement of over 300 feet. The principal Old Eureka vein occurs within the fault fracture zone. In the upper portions of the mine, the faulting has occurred along the contact between Mariposa Formation slate and greenstone resulting in a slate foot wall and greenstone hanging wall. Below the 1700-foot level, the foot wall remains slate but the hanging wall becomes a series of dense slaty greenstones. Foot wall slates dip 70? - 80? east and strike northwesterly. Wall rock slates are intensely folded and buckled adjacent to the faults. The associated hanging wall greenstones vary from highly metamorphosed fine grained volcanic to coarse-grained tuffs. Slates are intimately interbedded with the greenstones and transition zones are gradational (Norman, 1939). The gouge accompanying the fault varies in width from a few inches to 5 feet.

Three types of ore bodies occurred in the Old Eureka Mine: 1) fault ore bodies along the Wolverine fault consisting of irregular lenses of shattered quartz surrounded by gouge, 2) quartz veins in shear zones, and 3) bodies of mineralized greenstone or "gray ore" (Norman, 1939).
Rich ore bodies within the Wolverine Fault were the first ore bodies worked and the most productive. About $12 million was recovered from a 500 feet by 1700-foot ore shoot during early operations from 1852 to 1881. The richest part of the mine was about 1000 feet in depth, where the ore averaged $27 per ton. Elsewhere in the ore shoot values varied widely. In December, 1872, it averaged $35.19 per ton, and in December 1873 $6.65 per ton, averaging for 14 months $17.91 per ton (Logan, 1927). In the 1930s, small ore bodies along the same fissure were mined on the 2000, 2100, 2300, and 2500 foot north levels. The main Old Eureka vein consists mainly of milky white quartz with bands or ribbons of crushed wall rock slate. The bands are parallel to the walls and highly mineralized with pyrite and arsenopyrite. Ankerite, albite, sphalerite, chalcopyrite, and galena are present in lesser quantities. In places, intense crushing of the vein quartz is indicative of post mineralization movement along the fault. The bulk of the gold occurs as free milling gold, either in the quartz, in the ribbon structures, or around the borders of the pyrite (Norman, 1939). The vein varied in width from a few inches to 10 feet and the gouge a few inches to 3 feet. The quartz bodies were lenticular in shape, fraying out on the ends to a group of small quartz stringers where commercial values ended.

The second type of ore body occurs in quartz veins within shear zones that intersects the Wolverine fault at 20?, the largest being on the 2500-foot level 900 feet north of the shaft . A series of shear zone quartz stringers occur within slaty greenstone for about 500 feet north beyond the intersection before the quartz vein abruptly develops. The ore body from this point northward is 500 feet long. The vein strikes north while the Wolverine fault diverges from it, being 120 feet west at the south end of the ore body and 250 feet west at the north end. At the north end, the vein is vertical and on the south end it dips 70? east. The convergence of the strike and dip of the vein and fault with depth resulted in the truncation of the ore along a line that rakes north and shortens the ore body with depth. From the 2500-foot level to the 2900-foot level the width of the ore increases from an average of 8 feet to a maximum of 24 feet. The fault and vein are together on the 3000 foot level. Between the 3000 and 3100 foot sublevel, the major part of the fault gouge passes through the ore and on the 3300 foot sublevel, the fault is in the hanging wall greenstone (Norman, 1939).

Greenstone "gray ore" consisted of mineralized greenstone, most of which was developed in the hanging wall of the north drift on the 2100-foot level. Gray ore was usually adjacent to the veins in ground that has been fractured and contained small stringers and lenses of quartz. Alteration and replacement of the greenstone resulted in enough disseminated auriferous pyrite and arsenopyrite in large enough bodies to constitute low-grade ore. Gray ore Gold values are irregularly distributed in the greenstone, the pyrite and arsenopyrite content ranging from 2 to 5 percent (Norman, 1939).

Regional geologic features include the Bear Mountains Fault zone and the Melones Fault zone. Local features include the Melones Fault zone.

Workings include underground openings.

Due to its long history of operation and various owners, much detail about the underground workings of the Old Eureka Mine is lost ore unavailable. Further, after the consolidation of the mine's workings with the adjoining Central Eureka Mine, accounts get confusing regarding the various levels in each mine. Few if any records are available regarding the very early workings of the mine by poorly capitalized parties. The first "comprehensive" description of the mine is included in records of the California Division of Mines and Geology which describe the then current workings of the mine in June, 1929.

Prior to its acquisition by the Central Eureka Mining Company in 1924, the Old Eureka Mine consisted of a main 3500-foot shaft with levels at on the 800', 1200', 1700', 2100', 2950', and 3500-foot levels.

Drifts:
1700 foot level: North 740 feet, South 980 feet.
2100 foot level: North 480 feet, South 865 feet.
2950 foot level: North 720 feet, South 965 feet.

Crosscuts, raises, and winzes:
1700 foot level: hwcrosscut 385 feet. and fwcrosscut 425 feet south of shaft, and 2 crosscuts north of shaft
2100 foot level: 2 crosscuts 25 or 30 feet each north of shaft, and 2 crosscuts 30 or 40 feet south of shaft
2950 foot level: hwcrosscut north of shaft 235 feet and fwcrosscut 120 feet. Also fwcrosscut on south at face 40 feet and hwcrosscut 50 feet back from face, 30 feet long.
3500 foot level: crosscut 800 feet west

After acquisition by the Central Eureka Mining Company, drifts were run on the 2000', 2300', 2500' levels. The costs associated with mining small ore bodies from one level at a time necessitated the opening of the new ore on several levels simultaneously. The old shaft was cleaned out to the 3000-foot level and a drift was run northward 1800 feet and a raise driven to connect with a winze that had been started on the 2500-foot level. Sublevels were then run to several advantages levels.

During its later years while operated by the Central Eureka Mining Company, mining practices were modified from those in use in most Mother Lode mines. Development drifts were run in the harder hanging wall rocks instead of along the heavy swelling ground in the fissures. Timbering was suited to the actual needs, avoiding the old practice of heavy timbering throughout. Ore bodies were developed by driving haulage levels from the shaft at 500 foot intervals and using sub-levels to open sufficient stoping areas between for the economical mining of ore of a fairly constant value (Norman, 1939). Methods of exploration, stoping, general operations and milling details are provided by Norman (1939).

Production data are found in: Logan, Clarence August (1927), Amador County, Placer County: California Mining Bureau Report 23: 178.

Total production figures are not available but 12 to 13 million dollars (period values) is a fair estimate judging from the know output for several years. The richest part was 1,000 feet below surface where ore averaged $27 (period values) per ton. A 500 foot ore shoot bottomed between 1,700 and 1,800 with ore varying greatly. The average grade assayed $35 (period values) per ton.

Clark (1970) credited the Consolidated Central Eureka Mine (Central Eureka and Old Eureka mines) with a total production of $36 million (period values). Logan (1934) attributed $8.3 million of this amount to the original Central Eureka Mine before its consolidation with the Old Eureka mine and the cessation of work in the Central Eureka workings. Accordingly, the Old Eureka Mine property produced approximately $27.7 million (period values) prior to and after its merger with the Central Eureka.

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Link to USGS MRDS:	10028224

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