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La Grange District

Producer in Stanislaus 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 10310636
Record type District
Current site name La Grange District

Comments on the site identification

  • This district, which was primarily a dredge field, includes a 9-mile segment of the modern Tuolumne River between the towns of La Grange and Waterford. It also includes an area of older abandoned river channels about two miles south of La Grange.

Geographic coordinates

Geographic coordinates: -120.52958, 37.62782 (WGS84)
Location accuracy 100(meters)
Relative position The center of the La Grange District is about 26 miles east of the city of Modesto.

Site location context

Political divisions (FIPS codes)

Stanislaus(county)

California(state)

United States(country)

North America(continent)

Land(continent)

USGS map quadrangles

Cooperstown(quadrangle 1:24,000 scale)

Oakdale(quadrangle 1:100,000 scale)

San Jose(quadrangle 1:250,000 scale)

Hydrologic units (watersheds)

Lower San Joaquin River(hydrologic unit)

San Joaquin(hydrologic accounting unit)

San Joaquin(hydrologic subregion)

California(hydrologic region)

Geographic areas

Country State County
United States California Stanislaus

Public Land Survey System information

Meridian Township Range Section Fraction State
Mount Diablo 003S 013E 34 California

Comments on the location information

  • Location selected for latitude and longitude is the Mile 45 mark on the Tuolumne River on the USGS 7.5-minute Cooperstown quadrangle. This location represents approximately the half-way distance of the historic dredging activity along the river.

Commodities

Commodity Importance
Gold Primary
Platinum Critical Secondary
Silver Secondary

Comments on the commodity information

  • Commodity Info: Gold recovered was fine, but of good grade. Reported average yields during the 1920?s were about $0.12 per cubic yard.

    Platinum was about 2% of the total value recovered from dredging in the main field.
  • Ore Materials: Native gold, native platinum
  • Gangue Materials: Metamorphic rock, igneous rock, quartz (all as clasts)

Materials information

Materials Type of material
Gold Ore
Platinum 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
    Rock unit name Ione Formation
    Stratigraphic age (youngest) Tertiary
  • Host or associated Host
    Rock type Unconsolidated Deposit > Sand and Gravel
    Rock unit name Modesto Formation
    Stratigraphic age (youngest) Quaternary

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 La Grange District is situated within the Great Valley geologic province, which is here represented by the San Joaquin 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 La Grange District is associated with both modern alluvial deposits of the main drainage of the Tuolumne River where it discharges into the San Joaquin Valley after passing through the Sierra Nevada basement terranes and with older Tertiary alluvial deposits. 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 modern and Tertiary placer deposits along and adjacent to the Tuolumne River in the La Grange District.

    The dredging field south of La Grange appears to have exploited older alluvial channel deposits that may be both Quaternary and Tertiary in age. Geologic mapping of this area (Marchand and others, 1981) shows the presence of younger Quaternary alluvial deposits as well as older Tertiary sedimentary and volcanic deposits (Ione Formation, Valley Springs Formation, and Mehrten Formation). Gold-bearing gravels were likely present in both the Quaternary deposits and the Ione Formation.

Economic information about the deposit and operations

Operation type Surface-Underground
Development status Producer
Commodity type Metallic
Deposit size Medium
Significant Yes
Discovery year 1850

Mining district

District name La Grange District

Comments on the workings information

  • The district is composed mainly of one large dredge field about nine miles long and 1/2 mile wide along the Tuolumne River. The main dredging operation (La Grange Gold Dredging Company) reportedly processed over 70 million cubic yards of material during its activity in this field. A small dredge field is about two mile south of La Grange. Minor workings from surface placering and hydraulicking processes in the 1800?s were also present locally in the district.

    Vast deposits of dredge tailings still remain in this district.

Comments on other economic factors

  • Koschmann and Bergendahl (1968) reported about 108,000 ounces of gold produced from this district between !932 and 1959. Clark (1970) estimated that total production of gold for this district was approximately $13 million.

Comments on development

  • As published information about this district is sparse, it is uncertain exactly what year mining activity began in this district. Nonetheless, some surface placer mining and hydraulicking were done in La Grange area during the gold rush. The dominant production from the district came from dredging in the 20th century. This method of mining began in 1907 and continued intermittently until the 1950?s.

    Amalgamation was used in the recovery process.

    Gold is still being produced as a by-product of aggregate mining along the Tuolumne River.

Reference information

Bibliographic references

  • Deposit

    Charles, A., 1947, Mines and mineral resources of Stanislaus County: California Journal of Mines and Geology, v. 43, no. 2, p. 92-94.

  • Deposit

    Clark, W. B., 1970, Gold districts of California: California Divisions of Mines and Geology Bulletin 193, p. 85-86.

  • Deposit

    Higgins, C.T. and Dupras, D.L., 1993, Mineral land classification of Stanislaus County, California: California Division of Mines and Geology Special Report 173, 174 p.

  • 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

    Laizure, C.M., 1925, Stanislaus County: California State Mining Bureau 21st Report of the State Mineralogist, v. 21, no. 2, p. 200-222.

  • Deposit

    Laizure, C.M., 1935, Current mining activities in the San Francisco District with special reference to gold: California Journal of Mines and Geology, v. 31, no. 1, p. 48.

  • Deposit

    Marchand, D.E., Bartow, J.A. and Shipley, S., 1981, Preliminary geologic maps showing Cenozoic deposits of the Cooperstown and La Grange quadrangles, Stanislaus and Tuolumne Counties, California: U.S. Geological Survey Open-File Report 81-1049, scale 1:24,000.

  • Deposit

    Wagner, D.L., Bortugno, E.J., and McJunkin, R.D., 1990, Geologic map of the San Francisco-San Jose Quadrangle, California: California Department of Conservation, Division of Mines and Geology Regional Geologic Map Series, Map No. 5A, scale 1:250,000.

General comments

Subject category Comment text
Deposit In the main dredging field in and adjacent to the Tuolumne River, gold was recovered from Quaternary alluvial gravels and flood-plain and terrace deposits. The gravels are medium to coarse, loosely consolidated, and vary from about 10 to 40 feet in depth. Bedrock below the gravels is volcanic rock.

In the field south of La Grange, the ore material was very hard and overburden was up to 90 feet thick in places. Charles (1947) described the ore material as a Pleistocene river channel, but accompanying descriptions of overlying volcanic material suggest that at least some of the material was Tertiary in age, possibly Ione Formation.

Platinum is also present in the alluvial deposits.

Reporter information

Type Date Name Affiliation Comment
Reporter 09-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.

Maps centered on this site

Authoritative California resources

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