Hammonton District

Site Name

Primary: Hammonton District
Secondary: Yuba Gold Field
Secondary: Yuba River

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Commodity

Primary: Gold
Secondary: Sand and Gravel, Construction
Secondary: Platinum

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Location

State: California
County: Yuba
District: Hammonton District

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Land Status

Land ownership: BLM Administrative Area
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: Folsom Field Office

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Holdings

Not available

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Workings

Not available

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Ownership

Not available

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Production

Not available

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Deposit

Record Type: District
Operation Category: Producer
Deposit Type: Stream Placer
Operation Type: Surface
Discovery Year: 1849
Years of Production:
Organization:
Significant: Y
Deposit Size: L

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Physiography

Not available

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Mineral Deposit Model

Model Name: Placer Au-PGE

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Orebody

Form: Irregular

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Structure

Not available

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Alterations

Not available

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Rocks

Name: Sand and Gravel
Role: Host
Age Type: Host Rock
Age Young: Quaternary

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Analytical Data

Not available

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Materials

Ore: Gold
Ore: Platinum
Ore: Gravel
Ore: Sand
Gangue: Quartz

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Comments

Comment (Economic Factors): Koschmann and Bergendahl (1968) reported gold produced from this district through 1959 was about 4,387,000 ounces. Clark (1970) estimated that total production of gold for this district was at least $130 million as of the late 1960?s and 4.8 million ounces as of 1964. As of 1992, more than 5 million ounces of gold had been produced from this district (Cal Sierra Development, Inc., 1992). The recent period of operation was expected to annually produce about 20,000-25,000 ounces of gold per year.

Comment (Identification): This district comprises the extensive dredging field in Quaternary sediments along the Yuba River east of Marysville. It extends for approximately eight miles between a point about five miles northeast of Marysville to Long Bar. It is the most productive gold-dredging district in California and for many years was the principal source of gold in the state.

Comment (Location): Location selected for latitude and longitude is Daguerra Point on the USGS 7.5-minute Browns Valley quadrangle. This feature is not part of the dredge field itself, but represents an approximate center point of the field.

Comment (Geology): REGIONAL GEOLOGY The Hammonton District is situated within both the Sierra Nevada geologic province and the Great Valley geologic province, which is here represented by the Sacramento Valley. The Great Valley province is characterized by Cenozoic sedimentary and volcanic rocks, while the Sierra Nevada province is characterized by complex lithologies and structures that were assembled through various plate-tectonic processes. In this region, the Sierra Nevada province is composed of belts of Paleozoic-Mesozoic metamorphic complexes that are intruded by various Mesozoic plutons. Together, they compose the basement of the province. This basement is overlain at higher elevations by erosional remnants of Cenozoic volcanic and sedimentary rocks, including gravels. Most of these various lithologies contain gold in places. Structurally, the metamorphic rocks and some of the plutonic rocks have been deformed by folding and faulting. The major fault zones typically trend northerly or northwesterly, although in places intrusion of the younger plutons has deformed some of the zones so as to assume other trends as well. In contrast, the overlying Cenozoic rocks are relatively undeformed. The rocks of the Great Valley province overlie the basement of the Sierra Nevada where it extends westward underneath the San Joaquin Valley. LOCAL GEOLOGY The Hammonton District is associated with Cenozoic alluvial deposits of the main drainage of the Yuba River where it discharges into the Sacramento Valley after passing through the Sierra Nevada basement terranes. The materials in these deposits have been derived by erosion of the various basement and Cenozoic rocks at higher elevations. In places, the basement rocks contain gold within quartz veins and altered rock, while the Cenozoic deposits contain placer gold derived by erosion of these older basement rocks. Erosion of both the gold-bearing basement rocks and the older Cenozoic rocks provided the gold that was eventually deposited in the Cenozoic placer deposits along the Yuba River here at Hammonton. Some of these deposits are composed of debris that was washed down from the extensive hydraulic mining farther upstream in the watershed of the Yuba River. Platinum was probably derived from erosion of ultramafic rocks and serpentinite in the Sierra Nevada basement.

Comment (Commodity): Commodity Info: Minor amounts of platinum have been recovered from dredging. Sand and gravel for aggregate are produced as a by-product from dredging.

Comment (Commodity): Ore Materials: Native gold, native platinum, gravel and sand

Comment (Commodity): Gangue Materials: Metamorphic rock, igneous rock, quartz (all as clasts)

Comment (Deposit): The gravel is mostly medium-to-fine in particle size with few large boulders. It rests on metamorphic rock in the eastern part of the district and on clay in the central and western parts. The high-grade gravel occurs in streaks throughout the deposit. Most of these streaks are in the lower portion of the deposit near bedrock. The highest-grade portion of the deposit was the east, upstream part near the mouth of the Yuba River canyon.From here, the grade decreased and the pay streaks became deeper toward the southwest, or downstream, portion of the field. Little if any ground suitable for dredging is believed to be present west of the current downstream boundary of the field. Part of the material dredged consists of sediments washed down from the major hydraulic mines that were active in the Sierra Nevada during the mid to late 1800?s. ???????? (19 ) estimated that as much as 45 feet of the upper gravels are composed of this material.

Comment (Development): The Yuba River in this area was first worked by small-scale surface placering during the gold rush. Bucket-line dredging began in 1903. Dredging continued until 1968 when the last dredge stopped operation because of poor economic conditions. Dredging resumed with Dredge No. 21 in 1981 through a joint venture between Yuba Consolidated Goldfields and Placer Service Corporation. Cal Sierra Developments, Incorporated purchased Dredge No. 21 and all support assets and rights to minerals in 1992. In 2003, Dredge 21, the main dredge operated by Cal Sierra Development, sank out of sight in its 125-foot-deep pond. The cause was unknown at the time. To replace Dredge No. 21, Cal Sierra Development planned to obtain one of its sister dredges, No. 18, which was in Bolivia, South America. The Hammonton District is currently the site of controversy concerning public access versus private ownership at the site. Many dredges have operated in this district over the last century, and it has been the site of various innovations in the gold-dredging industry. Altogether, at least 21 separate dredges have operated in this field. Most of the district has been dredged at least twice and some areas three or four times, each time to a greater depth with more-efficient equipment for recovery. Natural replenishment of the field by the Yuba River has been curtailed since construction of Englebright Dam on the river in 1941. Amalgamation has been used in the recovery process. Also, mercury from the historic hydraulic mines is present in the deposits of this district. Vast deposits of dredge tailings still remain in this district. Some of them have been exploited as sources of aggregate, most recently by Western Aggregates, Inc..

Comment (Workings): Workings from small-scale placer mining were developed during the gold rush. The main workings of the district are those from dredging operations. More than a billion cubic yards of gold-bearing gravels have been dredged in this district. The tailings are present over a length of about eight miles and a width of up to about three miles. They are mostly on the south side of the present channel of the Yuba River. Maximum dredging depths ranged from 60-80 feet on the upstream end of the field to 100-125 feet at the downstream end of the field. Dredge No. 21, the most recently active dredge at the field, was capable of digging 140 feet below water level, which made it one of the deepest-digging dredges in the world. It processed about 4 million cubic yards of gravel annually. The processes of placer mining, including sections on dredging, are described in Averill (1946).

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References

Reference (Deposit): Winston, W.B., 1910, Gold dredging in California: California State Mining Bureau Bulletin 57, p. 164-174.

Reference (Deposit): Cal Sierra Development, Inc., 1992, Unpublished report on the Yuba Goldfields.

Reference (Deposit): O?Brien, J.C., 1952, Mines and mineral resources of Yuba County, California: California Journal of Mines and Geology, v. 48, no. 1, p. 143-179.

Reference (Deposit): Saucedo, G.J. and Wagner, D.L., 1992, Geologic map of the Chico Quadrangle, California: California Department of Conservation, Division of Mines and Geology Regional Geologic Map Series, Map No. 7A, scale 1:250,000.

Reference (Deposit): Averill, C.V., 1946, Placer mining for gold in California: California Division of Mines Bulletin 135, 377 p.

Reference (Deposit): Clark, W. B., 1970, Gold districts of California: California Divisions of Mines and Geology Bulletin 193, p. 62-63.

Reference (Deposit): Koschmann, A.H., and Bergendahl, M.H., 1968, Principal gold-producing districts of the United States: U. S. Geological Survey Professional Paper 610, 283 p.

Reference (Deposit): Lindgren, W., 1911, Tertiary gravels of the Sierra Nevada: U.S. Geological Survey Professional Paper 73, p. 221.

Reference (Deposit): Logan, C.A., 1919, Platinum and allied metals in California: California State Mining Bureau Bulletin 85, 120 p.

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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.