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Sweetwater Mine

Past Producer in San Luis Obispo county in California, United States with commodities Chromium, Platinum, Palladium, Iridium, Ruthenium, Rhodium
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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. Alteration
  9. Mineral occurrence model information
  10. Host and associated rocks
  11. Nearby scientific data
  12. Geologic structures
  13. Ore body information
  14. Controls for ore emplacement
  15. Economic information about the deposit and operations
  16. Land status
  17. Ownership information
  18. Production statistics
  19. Workings at the site
  20. Links to other databases
  21. Bibliographic references
  22. General comments
  23. Reporter information

Geologic information

Identification information

Deposit ID 10043681
MRDS ID M100580
Record type Site
Current site name Sweetwater Mine
Alternate or previous names San Juan Mine, Pierce and Benadom Group
Related records 10077397

Geographic coordinates

Geographic coordinates: -120.75459, 35.41803 (WGS84)
Elevation 472
Relative position ABOUT 17 MI NORTHWEST OF SAN LUIS OBISPO, ABOUT 6 MI EAST-NORTHEAST OF MORROW BAY

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 029S 011E 12,11 NE4 (11) California

Comments on the location information

  • IN LOS PADRES NATIONAL FOREST. ON SOUTHWEST SLOPE OF SANTA LUCIA RANGE. UTM PLACED ON LOWEST PART OF OPEN PIT. MINE IS ON AND E-W SPUR NEAR WEST END OF CUESTA RIDGE. LOCATION IS SHOWN AS MINE SYMBOL ON TOPO MAP

Commodities

Commodity Importance
Chromium Critical Primary
Platinum Critical Tertiary
Palladium Critical Tertiary
Iridium Critical Tertiary
Ruthenium Critical Tertiary
Rhodium Critical Tertiary

Materials information

Materials Type of material
Chromite Ore
Antigorite Gangue
Picotite Gangue
Spinel Gangue

Alteration

  • (Local) Dunite Is Serpentinized

Analytical data

Result 2 PGE ANALYSES: PT=10, 10 PPB
Result PD=2, 2 PPB
Result IR=170, 50 PPB
Result RU=400, <100 PPB
Result RH=8, 2 PPB. AVE CR:FE=2.61:1. CRUDE ORE AVE 35% CR2O3, CONCENTRATES AVE 52% CR2O3.

Mineral occurrence model information

Model code 15
USGS model code 8a
Deposit model name Podiform chromite (minor)
Mark3 model number none

Host and associated rocks

  • Host or associated Associated
    Rock type Plutonic Rock > Ultramafic Intrusive Rock > Peridotite
    Rock unit name Coast Range Ophiolite
    Rock description Coast Range Ophiolite
    Stratigraphic age (youngest) Late Jurassic
    Stratigraphic age (youngest) Late Jurassic
    Stratigraphic age (youngest) Late Jurassic
  • Host or associated Host
    Rock type Plutonic Rock > Ultramafic Intrusive Rock > Peridotite > Dunite

Economic information

Geologic structures

Type of structure Local
Structure description Prevalent Shearing

Ore body information

  • General form PODS, STREAKS, CLOTS, DISCRETE GRAINS, KIDNEY SHAPED BODIES
    Strike N25W
    Dip 45-60NE
    Thickness 9.14M
    Length 60.96M

Controls for ore emplacement

  • Magmatic Segregation

Economic information about the deposit and operations

Development status Past Producer
Commodity type Metallic
Deposit size Small
Significant No
Year of first production 1885

Land status

Ownership category National Forest

Ownership information

  • Type Operator
    Owner Ruda And Negranti, J. D. Hoffman, Harry Stevens
    First year 1957
  • Type Owner
    Owner Pierce, W. W.
    First year 1953

Production statistics

  • Year 1950
    Period 1880-1950
    Material ORE
    Accuracy Accurate
    Description Cp_Grade: ^46% Cr2o3
    Importance Item Commodity Group Amount recovered Grade Recovery percentage
    Major Cr2O3 Chromium Chromium 46wt-pct

Workings at the site

  • Type of workings Surface/Underground
    Length 426.72M
    Overall depth 60.96M
    Overall length 228.6M
    Overall width 60.96M

Comments on the workings information

  • 5 OPEN PITS OVER 325 FT DISTANCE, RUNNING N60W; 5 TUNNELS AND CROSSCUTS USED UNTIL THE 1950'S

Comments on development

  • USBM EVALUATED MINE AND ASSAYED 162 SAMPLES IN 1941

Reference information

Bibliographic references

  • Deposit

    WALKER, G.W., AND GRIGGS, A.B., 1953, GEOLOGICAL INVESTIGATIONS OF CHROMITE IN CALIFORNIA: CALIFORNIA DIVISION OF MINES BULLETIN 134, PT. 2, CH. 2, P. 48, 67.

  • Deposit

    CARLSON, C.A., AND OTHERS, 1985, ANALYSES FOR PLATINUM-GROUP ELEMENTS IN SAMPLES FROM PODIFORM CHROMITE DEPOSITS, CALIFORNIA AND OREGON: U.S. GEOLOGICAL SURVEY OPEN-FILE REPORT 85-442, 14 P.

  • Deposit

    STINSON, M.C., 1975, CALIFORNIA DIVISION OF MINES AND GEOLOGY MINERAL PROPERTY REPORT, UNPUB.

  • Deposit

    SMITH, C.T., AND GRIGGS, A.B., 1944, CHROMITE DEPOSITS NEAR SAN LUIS OBISPO, SAN LUIS OBISPO COUNTY, CALIFORNIA: U.S. GEOLOGICAL SURVEY BULLETIN 945-B, P. 36-37.

  • Deposit

    BRADLEY, W.W., HUGUENIN, EMILE, LOGAN, C.A., TUCKER, W.B., AND WARING, C.A., 1918, MANGANESE AND CHROMIUM IN CALIFORNIA: CALIFORNIA STATE MINING BUREAU BULLETIN 76, P. 177-178.

  • Deposit

    ALLEN, J.E., 1941, GEOLOGICAL INVESTIGATION OF THE CHROMITE DEPOSITS OF CALIFORNIA: CALIFORNIA JOURNAL OF MINES AND GEOLOGY V. 37, NO. 1, P. 140.

  • Production

    STINSON, 1975

General comments

Subject category Comment text
Deposit LARGEST DEPOSIT IN GROUP. THERE ARE 600 FT OF CHROME OUTCROPS OVER A VERTICAL RANGE OF 150 FT. FORMED BY SEVERAL SEPARATE ORE BODIES
Deposit RECORD W025008 HAS BEEN MERGED AND DELETED.

Reporter information

Type Date Name Affiliation Comment
Reporter 01-MAR-1982 Oster, Karel L. (Albers, John P.) U.S. Geological Survey
Updater 01-FEB-1990 Peterson, Jocelyn A. U.S. Geological Survey

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.