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Folsom District

Producer in Sacramento county in California, United States with commodities Gold, Platinum, Silver
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Sections on this page
  1. Identification information
  2. Geographic coordinates
  3. Site location context
  4. Geographic areas
  5. Public Land Survey System information
  6. Commodities
  7. Materials information
  8. Mineral occurrence model information
  9. Host and associated rocks
  10. Nearby scientific data
  11. Ore body information
  12. Controls for ore emplacement
  13. Economic information about the deposit and operations
  14. Mining district
  15. Bibliographic references
  16. General comments
  17. Reporter information

Geologic information

Identification information

Deposit ID 10310613
Record type District
Current site name Folsom District

Comments on the site identification

  • The Folsom District is one of the two largest dredging fields in California. It extends along the American River from the city of Folsom southwestward for about 10 miles to the community of Rancho Cordova.

Geographic coordinates

Geographic coordinates: -121.21143, 38.62323 (WGS84)
Location accuracy 100(meters)
Relative position The Folsom District is appoximately 16 miles east-northeast of downtown Sacramento.

Site location context

Political divisions (FIPS codes)

Sacramento(county)

California(state)

United States(country)

North America(continent)

Land(continent)

USGS map quadrangles

Buffalo Creek(quadrangle 1:24,000 scale)

Sacramento(quadrangle 1:100,000 scale)

Sacramento(quadrangle 1:250,000 scale)

Hydrologic units (watersheds)

Lower American(hydrologic unit)

Lower Sacramento(hydrologic accounting unit)

Sacramento(hydrologic subregion)

California(hydrologic region)

Geographic areas

Country State County
United States California Sacramento

Public Land Survey System information

Meridian Township Range Section Fraction State
Mount Diablo 009N 007E 21 California

Comments on the location information

  • Location selected for latitude and longitude is the intersection of Buffalo Creek with Nimbus Road south of US Highway 50 on the USGS 7.5-minute Buffalo Creek quadrangle. This location approximates the center of the regional dredging area.

Commodities

Commodity Importance
Gold Primary
Platinum Critical Secondary
Silver Secondary

Comments on the commodity information

  • Commodity Info: Recoveries of gold ranged from about $0.10 to $0.20 per cubic yard at $35/oz. Carlson (1955).
    Carlson (1955) reported that platinum recovery from dredging operations in California ranged from 1/3 to one ounce for every 50 ounces of gold. Logan (1919) reported that about 150 ounces of platinum were produced from dredging annually during 1914-1916.
  • Ore Materials: Native gold, native platinum, electrum
  • Gangue Materials: Metamorphic rock, igneous rock, quartz (all as clasts)

Materials information

Materials Type of material
Gold Ore
Platinum Ore
Electrum Ore
Quartz Gangue

Mineral occurrence model information

Model code 119
USGS model code 39a
Deposit model name Placer Au-PGE
Mark3 model number 54

Host and associated rocks

  • Host or associated Host
    Rock type Unconsolidated Deposit > Sand and Gravel
    Stratigraphic age (youngest) Quaternary

Nearby scientific data

(1) -121.21143, 38.62323
ListMap

Economic information

Ore body information

  • General form Irregular

Controls for ore emplacement

  • Mechanical accumulation within stream-channel lag gravels, bars, and point-bar deposits.

Comments on the geologic information

  • REGIONAL GEOLOGY

    The Folsom District is situated within the Great Valley geologic province, which is here represented by the Sacramento Valley. It is adjacent to the westernmost edge of the Sierra Nevada geologic province.

    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 Folsom District is associated with Cenozoic alluvial deposits of the main drainage of the American 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 American River at Folsom and farther downstream. Platinum was probably derived from erosion of ultramafic rocks and serpentinite in the Sierra Nevada basement.

Economic information about the deposit and operations

Operation type Surface-Underground
Development status Producer
Commodity type Metallic
Deposit size Large
Significant Yes
Discovery year 1849

Mining district

District name Folsom District

Comments on the workings information

  • Early workings in this district consisted of those from surface-placer methods, hydraulicking, and drift mining. The area mined by dredging is about 10 miles long in a southwest direction and up to seven miles wide. Digging depths ranged from about 30 to 110 feet. Approximately one billion cubic yards of gravel were dredged by the Natomas Company alone.

    Vast deposits of dredge tailings still remain in this district.

Comments on other economic factors

  • Koschmann and Bergendahl (1968) reported gold produced from this district was at least 3 million ounces. Clark (1970) estimated that total production of gold for this district was approximately $125 million.

Comments on development

  • The region around the city of Folsom was extensively placer-mined during the gold rush and continued through the 1890?s. Carlson (1955) reported some hydraulicking and drifting along older Cenozoic channels in the Folsom area before 1900, with drift mining continuing into the early 1900?s. Dredging began in a minor way in 1894, but became a major activity after 1898 and continued until 1962. The dominant gold production in the district was from dredging. Production of platinum as a by-product of dredging began in 1905 (Carlson, 1955).

    Amalgamation was used in the recovery process.

    Platinum was recovered as a by-product of dredging since 1905. Gold is still being recovered as a by-product from aggregate mining in similar geologic materials adjacent to this district.

Reference information

Bibliographic references

  • Deposit

    Clark, W. B., 1970, Gold districts of California: California Divisions of Mines and Geology Bulletin 193, p. 47-48.

  • Deposit

    Carlson, D.W., 1955, Mines and mineral resources of Sacramento County, California: California Journal of Mines and Geology, v. 51, no. 2, p. 134-143.

  • 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.

  • Deposit

    Lindgren, W., 1911, Tertiary gravels of the Sierra Nevada: U.S. Geological Survey Professional Paper 73, p. 222.

  • Deposit

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

  • Deposit

    Wagner, D.L. and others, 1981, Geologic map of the Sacramento Quadrangle, California: California Department of Conservation, Division of Mines and Geology Regional Geologic Map Series, Map No. 1A, scale 1:250,000.

  • Deposit

    Winston, W.B., 1910, Gold dredging in California: California State Mining Bureau Bulletin 57, p. 175-204.

General comments

Subject category Comment text
Deposit Gold was recovered from Tertiary and Quaternary alluvial gravels and flood-plain and terrace deposits in and adjacent to the American River. The gold-bearing gravels are found chiefly near the bases of certain Plio-Pleistocene terraces and near the contact of the Laguna Formation with the underlying Mehrten Formation (Carlson, 1955). These settings have been exploited mainly south of the river.

Platinum is also present in the alluvial deposits.

Reporter information

Type Date Name Affiliation Comment
Reporter 08-AUG-2006 Higgins, Chris T. California Geological Survey CGS (Formerly CDMG)
Editor 01-SEP-2007 Schruben, Paul G. U.S. Geological Survey Converted from S&A FileMaker format to Oracle. Edit checks on rocks, units, and ages with Geolex search, and other fields.

Beyond USGS

Supplemental information added by qvyshift.com. Not part of the original USGS MRDS record.

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Authoritative California resources

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