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Sweetwater Chromite Mine

Past Producer in San Luis Obispo county in California, United States with commodity Chromium
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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. Nearby scientific data
  9. Ore body information
  10. Economic information about the deposit and operations
  11. Mining district
  12. Mineral rights holdings
  13. Land status
  14. Ownership information
  15. Production statistics
  16. Workings at the site
  17. Links to other databases
  18. Bibliographic references
  19. Reporter information

Geologic information

Identification information

Deposit ID 10286725
MRDS ID W025008
MAS/MILS ID 0060790032
Record type Site
Current site name Sweetwater Chromite Mine
Alternate or previous names San Juan Mine, Sweetwater Chrome Mine, San Juan Chrome Mine, Pierce and Benadon Group

Geographic coordinates

Point of reference Ore Body
Geographic coordinates: -120.75428, 35.41827 (WGS84)
Elevation 476
Location accuracy 10(meters)

Site location context

Political divisions (FIPS codes)

San Luis Obispo(county)

California(state)

United States(country)

North America(continent)

Land(continent)

USGS map quadrangles

Morro Bay North(quadrangle 1:24,000 scale)

San Luis Obispo(quadrangle 1:100,000 scale)

San Luis Obispo(quadrangle 1:250,000 scale)

Hydrologic units (watersheds)

Central Coastal(hydrologic unit)

Central California Coastal(hydrologic accounting unit)

Central California Coastal(hydrologic subregion)

California(hydrologic region)

Federal lands

Los Padres National Forest(National Forest)

National Forest FS(Type of land area)

FS(Federal land areas administered by FS)

Geographic areas

Country State County
United States California San Luis Obispo

Public Land Survey System information

Meridian Township Range Section Fraction State
Mount Diablo 029 S 011 E 12 NWNWSW California

Commodities

Commodity Importance
Chromium Critical Primary

Materials information

Materials Type of material
Chromite Unknown
Magnetite Unknown
Olivine Unknown
Pyroxene Unknown
Serpentine Unknown

Nearby scientific data

Ore Body (1) Franciscan Complex, unit 1 (Coast Ranges)
ListMap

Economic information

Ore body information

  • Strike N60W
    Dip 50N
    Thickness 6M
    Length 200M
    Width 50M
    Area 5HA
    Depth to top 0M
    Field Value
    Type of Orebody #1 DISSEMINATED
    Shape of Orebody #1 TABULAR
    Type of Orebody #2 SHEAR ZONE
    Shape of Orebody #2 LENTICULAR
    Shape of Orebody #3 IRREGULAR
    Primary mode of Origin MAGMATIC DIFFER
    Primary Ore Control LITHOLOGY
    Degree of Wallrock Alter. INTENSE
    Type of Wallrock Alter. #1 CARBONITIZATION
    Strike And Dip N60W:50N
    Minimum Depth to Top 0
    Avg. Thick. Unconsol. Mat. 0
    Min. Thick. Unconsol. Mat. 0
    Total Surface Area (HA) 5
    Date of Last Modification 820524

Economic information about the deposit and operations

Operation type Surface-Underground
Development status Past Producer
Commodity type Metallic
Significant No
Discovery year 1880
Year of first production 1917

Mining district

District name Cerro Alto-Cuesta Pass Area

Mineral rights holdings

Type of mineral rights Patented
Type of mineral rights Private Lease

Land status

Ownership category Private

Ownership information

  • Type Owner
    Owner San Juan Chrome-Conflicting Owner-Ship Data
    Home office California
    Year 1976
  • Type Owner
    Owner U.S. Forest Service - Los Padres National Forest
    Home office California
    Year 1976
  • Type Operator
    Owner John D. Hoffman-One Of Last Operators In 1957
    Home office California
    Year 1976
  • Type Operator
    Owner Ruda And Negranti-Also Operated Minein 1955-1957
    Home office California
    Year 1976

Production statistics

  • Year 1928
    Description Concentrates Produced From 1928-1930'S. 1039 Mt @ 46 Pct
  • Year 1950
    Description Lump Ore Produced In 1950'S. 120 Mt
  • Year 1950
    Description Concentrates Produced In 1950'S. 4500 Mt @ 52 Pctt-2.6:1 Cr:Fe
  • Year 1950
    Description Ore Mined In 1950'S. 13600 Mt

Comments on the reserve resource information

  • MAT 1 COL 1 REPRESENTS TOTAL RESOURCES MAT 1 COL 2 REPRESENT HIGH GRADE ORE MAT 1 COL 3 REPRESENTS LOW GRADE ORE
  • NO RESERVE ESTIMATE BY USBM OR USGS. ASSAY FROM USGS CR/FE AVERAGES 2.26/1% CR2O3 CONCENTRATE 52. ORE RAN 35%. INSUFFICIENT DATA FOR MATRIX CALCULATIONS ANALYSIS BY CDMG IN 1976 GAVE FOLLOWING PERCENTAGES-DISSEMIN E=SI02 07.36,CR2O3 42.39,FEO 15.17,TOTAL FE 14.95,AL203 16.5 0.78,CR/FE 1.87

Workings at the site

  • Type of workings Surface
    Area 1HA
    Field Value
    MAS Development Schedule # 1
    Mining Record # 1
    Mining Method OPEN PIT
    Swell Factor .6
    Hardness of Ore M-HARD ROCKS
    Avg. Bench Height (meters) 20
    Max. Pit Slope (degrees) 60
  • Type of workings Underground
    Length 426M
    Field Value
    MAS Development Schedule # 1
    Mining Record # 1
    Mining Method OVERHAND 10-38
    Swell Factor .6

Reference information

Bibliographic references

  • Deposit

    CALIF. STATE MINING BUR. BULLETIN 76, 1918, P. 177-178.

  • Deposit

    CALIF. JOUR. MINES AND GEOL. V. 37, 1941, P. 140.

  • Deposit

    U.S. GEOLOGICAL SURVEY BULLETIN 945-B, 1944, P. 36-37.

  • Deposit

    U.S. BUREAU OF MINES RI 4783, 1951, P. 3-4.

  • Deposit

    CALIF. DIV. MINES BULLETIN 134, 1953, PART II, CHAPT. 2,

  • Deposit

    P. 67.

Reporter information

Type Date Name Affiliation Comment
Reporter 18-AUG-1992 Wetzel, Nicholas U.S. Bureau of Mines

Beyond USGS

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

Maps centered on this site

Authoritative California resources

These are landing pages for further research — the state agencies don't currently expose per-mine deep links.