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Dobbas Mine

Past Producer in El Dorado county in California, United States with commodities Chromium, Iron
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Geologic information

Identification information

Deposit ID 10043721
MRDS ID M100633
Record type Site
Current site name Dobbas Mine

Geographic coordinates

Geographic coordinates: -120.07878, 38.79712 (WGS84)
Elevation 280
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Geographic areas

Country State County
United States California El Dorado

Public Land Survey System information

Meridian Township Range Section Fraction State
Mount Diablo 011N;011N;011N 008E;008E;008E 15;16;22 W2 (15); E2 (16); NW OF NW (22) California

Commodities

Commodity Importance
Chromium Primary
Iron Tertiary

Comments on the commodity information

  • ORE HAS VERY HIGH IRON CONTENT

Materials information

Materials Type of material
Magnesite Gangue
Magnetite Gangue

Alteration

  • (Local) Much Of Ultramafic Rock Altered To Talc Chlorite Or Talc Serpentine.

Analytical data

Result ORE RANGES 6-30% CR2O3, CR: FE RATIO 0.67

Host and associated rocks

  • Host or associated Associated
    Rock type Plutonic Rock > Mafic Intrusive Rock > Diorite
  • Host or associated Associated
    Rock type Plutonic Rock > Ultramafic Intrusive Rock > Peridotite > Harzburgite
  • Host or associated Associated
    Rock type Plutonic Rock > Ultramafic Intrusive Rock > Pyroxenite
  • Host or associated Host
    Rock type Plutonic Rock > Ultramafic Intrusive Rock > Peridotite > Dunite
  • Host or associated Host
    Rock type Metamorphic Rock > Serpentinite

Nearby scientific data

(1) -120.07878, 38.79712
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Geologic structures

Type of structure Local
Structure description Ore In Area C Cut By Vertical, Ew Striking Faults.

Ore body information

  • General form IRREGULAR PODS AND LENSES
    Width 243.84M
    Length 1609.3M

Comments on the geologic information

  • DEPOSIT LOCATED NEAR NORTHERN END OF ELONGATED N-S TRENDING ULTRAMAFIC MASS APPROX 5 MILES LONG AND 1 MILE WIDE, WHICH FORMS FLAGSTAFF HILL. MOST OF THE ORE BODIES TREND N TO NW, ROUGHLY PARALLEL TO THE EASTERN MARGIN OF THE ULTRAMAFIC MASS, AND LIE FROM 200 FT TO 1000 FT WEST OF THE CONTACT.

Economic information

Economic information about the deposit and operations

Development status Past Producer
Commodity type Metallic
Deposit size Small
Significant No

Mining district

District name Flagstaff Hill Area

Land status

Ownership category Private

Comments on the reserve resource information

  • LARGE RESERVES MAY BE OF LITTLE ECONOMIC VALUE BECAUSE OF HIGH IRON CONTENT OF CHROMITE.

Comments on the workings information

  • DOBBAS MINE CONSISTS OF WORKINGS, DIVIDED INTO 5 GROUPS, A THROUGH E, WHICH EXTEND APPROX A MILE ALONG A RIDGE N FROM FLAGSTAFF HILL. AREA A CONSISTS OF 3 OPEN CUTS, AND AN ADIT. UNDERGROUND WORKINGS INACCESSIBLE. APPROX 1 TON "HIGH-GRADE" DISSEMINATED ORE PILED ON DUMP. AREA B INCLUDES 6 OLD PITS AND ONE NEW PIT. ORE IN NEW PIT STRIKES N 30 W AND DIPS STEEPLY TO EAST. AREA C CONSISTS OF 10 PITS OR CUTS, TWO ADITS AND ONE SHAFT. LAYERS OF CHROMITE STRIKE N 45 W. AREA D IS WORKED B4 A NUMBER OF TRENCHES. ORE STRIKES N 20 W AND DIPS 75 E. AREA E CONSISTS OF AN OPEN CUT AND A NUMBER OF EXPLORATORY TRENCHES. ORE STRIKES N 60 W AND DIPS 60 N.

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Mineral Resources Data System MRDS M100633

Bibliographic references

  • Deposit

    CDMG BULL 134, P. 146-148

  • Deposit

    STINSON, M.C., 1976, MINERAL PROPERTY REPORT, CDMG UNPUBLISHED REPORT.

  • Production

    CDMG BULL 134, P. 110

General comments

Subject category Comment text
Deposit MINERALIZED ZONE'S DIMENSIONS GIVEN ABOVE.

Reporter information

Type Date Name Affiliation Comment
Reporter 01-JUL-1980 Oster, Karel L. (Albers, John P.) U.S. Geological Survey