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Benbow Mine

Past Producer in Stillwater county in Montana, United States with commodities Chromium, Iron
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Geologic information

Identification information

Deposit ID 10197365
MRDS ID MO60101
MAS/MILS ID 0300950004
Record type Site
Current site name Benbow Mine
Alternate or previous names Benbow Chromite Deposit

Comments on the site names

  • PART OF STILLWATER COMPLEX.

Geographic coordinates

Point of reference Main Entrance
Geographic coordinates: -109.8061, 45.3642 (WGS84)
Elevation 2575
Location accuracy 10(meters)
(click for info)

Geographic areas

Country State County
United States Montana Stillwater

Public Land Survey System information

Meridian Township Range Section Fraction State
Montana Principal 005 S 016 E 30 SWSWSW Montana

Commodities

Commodity Importance
Chromium Primary
Iron Tertiary

Materials information

Materials Type of material
Bronzite Unknown
Chromite Unknown
Enstatite Unknown
Forsterite Unknown
Olivine Unknown

Nearby scientific data

Main Entrance (1) -109.8061, 45.3642
ListMap

Ore body information

  • Strike N70N
    Dip 95N
    Thickness 1.5M
    Depth to top 0M
    Width 1859M
    Length 2743M
    Area 56HA
    Field Value
    Type of Orebody #1 OTHER
    Shape of Orebody #1 TABULAR
    Shape of Orebody #2 IRREGULAR
    Primary mode of Origin MAGMATIC DIFFER
    Primary Ore Control IGNEOUS
    Degree of Wallrock Alter. NONE
    Type of Wallrock Alter. #1 UNKNOWN
    Strike And Dip N70N
    Minimum Depth to Top 0
    Avg. Thick. Unconsol. Mat. 0
    Min. Thick. Unconsol. Mat. 0
    Total Surface Area (HA) 56
    Date of Last Modification 830316

Comments on the geologic information

  • CR:FE RATIO AVERAGES 1.72:1 CHEMICAL ANALYSIS OF REPRESENTATIVE SAMPLE (USBM RI 6448, 1964).: HEAD MINERAL CR2O3 7.75 42.6 FE 9.72 19.2 SI02 33.4 1.24 CAO .50 .10 MGO 29.5 11.8 AL203 4.88 17.0
  • OREBODY TYPE- ORIGINAL ROCK FORMING MINERAL. ALTERATION- SERPENTINIZATION IN FAULTED AREAS.

Economic information

Economic information about the deposit and operations

Operation type Underground
Development status Past Producer
Commodity type Metallic
Significant Yes
Discovery year 1918
Year of first production 1941

Mining district

District name Stillwater

Mineral rights holdings

Type of mineral rights Patented

Land status

Ownership category National Forest

Ownership information

  • Type Unknown
    Owner Bill Mouat Estate
    Interest 100
    Home office Montana
    Year 1988
  • Type Owner-Operator
    Owner Boulder Gold, N. L.
    Home office Colorado
    Year 1988

Comments on the production information

  • FROM 1941 TO 1943, THE ANACONDA CO. HAD MINED FROM BENBOW 203800 MT OF ORE AND MILLED 169170 MT TO PRODUCE 65831 MT OF CONCENTRATE AVERAGING 41.5 PERCENT CR2O3. PRODUCTION WAS HALTED BY GOVERNMENT ORDER AS HIGHER-GRADE, FOREIGN CHROMITE ORES BECAME AVAILABLE.

Reserves and resources

  • Type In-situ
    Estimate year 1937
    Demonstrated 1,090,000mt ore
    Indicated 1,090,000mt ore
    Total resources 1,090,000mt ore
    Commodity Subtype Grade units Group Importance Year
    Chromium Cr2O3 29.82 wt-pct Chromium Major 1937
  • Type In-situ
    Estimate year 1940
    Demonstrated 1,518,000mt ore
    Indicated 1,338,000mt ore
    Measured 180,000mt ore
    Total resources 1,518,000mt ore
    Commodity Subtype Grade units Group Importance Year
    Chromium Cr2O3 25.6 wt-pct Chromium Major 1940
  • Type In-situ
    Estimate year 1940
    Demonstrated 313,000mt ore
    Indicated 313,000mt ore
    Total resources 313,000mt ore
    Commodity Subtype Grade units Group Importance Year
    Chromium Cr2O3 11.8 wt-pct Chromium Major 1940
  • Type In-situ
    Estimate year 1980
    Demonstrated 17,400,000mt ore
    Total resources 17,400,000mt ore
    Commodity Subtype Grade units Group Importance Year
    Chromium Cr2O3 23 wt-pct Chromium Major 1980

Comments on the reserve resource information

  • THE MAS RESOURCE MATRIX ONE IS PREDICATED ON BUREAU OF MINES MEASUREMENTS OF ORE BLOCKS DEVELOPED BY THE ANACONDA MINING CO. IN 1941-1943. THE MEASURED AND INDICATED(DEMON- STRATED) ORE CATEGORIES WERE INCREASED TO INCLUDE ALL ORE ABOVE THE PROPOSED NO. 6 LEVEL AT WEST BENBOW AND ABOVE 8,100 FEET (2,469 M) ELEVATION AT EAST BENBOW. ADDITIONAL IDENTIFIED ORE WAS INFERRED TO 7,100 FEET (2,164 M) ELE- VATION, THE LOWEST CHROMITE SURFACE EXPOSURE ON THE MOUAT PROPERTY. A POTENTIAL RESOURCE UNDER CENTRAL BENBOW WAS NOT ESTIMATED, AS A LARGE SHEAR ZONE EXISTS, RESULTING IN MAJOR DILUTION AND GROUND SUPPORT PROBLEMS. THE ORE GRADE WAS DETERMINED BY UNDERGROUND SAMPLING AND VOLUME AVERAGING AND DOES NOT COMPENSATE FOR DILUTION. MINE RUN ORE IS ESTIMATED AT 22.0 PERCENT CR2O3. CR:FE RATIO AVERAGES 1.72:1.

Comments on the workings information

  • MINE ROAD LENGTH - 11 KM ELECTRICAL SOURCE - 14 KM WATER SOURCE - ON SITE ENVIRONMENTAL DISTURBANCE MINIMAL - SURFACE FACILITIES RE- STRICTED TO PREVIOUS MINE SITE, ROADS, ETC.

Comments on other economic factors

  • TRANSPORTATION COSTS- TRUCK HAUL= $2.71/ TONNE RAIL HAUL= $22.428/ TONNE
  • PROPOSED TO START UP IN 1993. FROM 1941-43 COMPANY MINED 203,800 MT ORE, MILLED 169,170 MT ORE AND PRODUCED 65,831 MT CONCENTRATE. AT 41.5 PCT CR2O3; CR:FE RATIO AVERAGES 1.72;1.0.

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
U.S. Bureau of Mines Minerals Availability System MAS 0300950004
USGS Mineral Resources Data System MRDS MO60101 MAS references MRDS

Bibliographic references

  • Geology

    JACKSON, E.D., A.L. HOWLAND, J.W. PEOPLES, AND W.R. JONES.

  • Geology

    GEOLOGICAL MAPS AND SECTIONS OF THE EASTERN PART OF

  • Geology

    THE STILLWATER COMPLEX IN STILLWATER COUNTY, MONTANA. U.S.

  • Geology

    GEOLOGICAL SURVEY OPEN FILE RPT., 1954, 3 MAPS, 14 SECTIONS.

  • Production

    BOERICKE, F.S. AND W.M. BANGERT. EFFECT OF VARIABLES IN

  • Production

    CHEMICAL BENEFICIATION OF CHROMITE ORES. U.S. BUR OF MINES

  • Production

    R.I. 3817, 1945, 26 PP.

  • Production

    HUNTER, WILLARD L. AND LLOYD H. BANNING. PYROMETALLURGICAL

  • Production

    BENEFICIATION OF OFF-GRADE CHROMITE AND PRODUCTION OF FER-

  • Production

    ROCHROMIUM. U.S. BUR OF MINES R.I. 6010, 1962, 16 PP.

  • Production

    SULLIVAN, G.V. AND W.A. STICKNEY. FLOTATION OF PACIFIC

  • Production

    NORTHWEST CHROMITE ORES. U.S. BUR OF MINES R.I. 5646, 1960

  • Production

    14 PP.

  • Production

    SULLIVAN, G.V. AND G.F. WORKENTINE. BENEFICATING LOW-

  • Production

    GRADE CHROMITES FROM THE STILLWATER COMPLEX, MONTANA. U.S.

  • Production

    BUR OF MINES R.I. 6448. 1964, 29 PP.

  • Geology

    HESS, H.H. STILLWATER IGNEOUS COMPLEX, MONTANA. GEOL. SOC.

  • Geology

    AMER. MEM. 80, 1966, 230 PP.

  • Geology

    JACKSON, E.D. PRIMARY TEXTURES AND MINERAL ASSOCIATIONS IN

  • Geology

    THE ULTRAMAFIC ZONE OF THE STILLWATER COMPLEX, MONTANA.

  • Geology

    U.S. GEOLOGICAL SURVEY PROF. PAPER 358, 1961, 106 PP.

  • Geology

    JACKSON, E.D. STRATIGRAPHIC AND LATERAL VARIATION OF CHRO-

  • Geology

    MITE COMPOSITION IN THE STILLWATER COMPLEX. MIN. SOC.

  • Geology

    AMER. SPEC. PAPER 1, 1963, PP. 46-54.

  • Reserve-Resource

    PEOPLES, J.W., AND A.L. HOWLAND. CHROMITE DEPOSITS OF THE

  • Reserve-Resource

    EASTERN PART OF THE STILLWATER COMPLEX, STILLWATER COUNTY,

  • Reserve-Resource

    MONTANA. U.S. GEOLOGICAL SURVEY BULL. 922-N, 1940, PP. 371-416.

  • Reserve-Resource

    SCHAFER, P.A. CHROMITE DEPOSITS OF MONTANA. MONTANA BUR. OF

  • Reserve-Resource

    MINES AND GEOL. MEM. 18, 1937, 35 PP.

  • Deposit

    ANONYMOUS. CHROMIUM MATERIALS SURVEY. U.S. DEPT. COMMERCE,

  • Deposit

    1962, 96 PP.

  • Deposit

    JACKSON, E.D. THE CHROMITE DEPOSITS OF THE STILLWATER SOM-

  • Deposit

    PLEX, MONTANA. IN ORE DEPOSITS IN THE U.S., 1933-1967,

  • Deposit

    (GRATON SALES), V. 2, NEW YORK, AIME, 1968, PP. 1495-1510.

  • Deposit

    JONES, W.R., J.W. PEOPLES, AND A.L. HOWLAND. IGNEOUS AND

  • Deposit

    TECTONIC STRUCTURE OF THE STILLWATER COMPLEX, MONTANA.

  • Deposit

    U.S. GEOLOGICAL SURVEY BULL. 1071-H, 1960, PP. 281-340.

  • Deposit

    PAGE, N.J., AND J.C. DOHRENWEND. MINERAL RESOURCE POTEN-

  • Deposit

    TIAL OF THE STILLWATER COMPLEX AND ADJACENT ROCKS IN THE

  • Deposit

    NORTHERN PART OF THE MT. WOOD AND MT. DOUGLAS QUADRANGLES,

  • Deposit

    SOUTHWESTERN MONTANA. U.S. GEOLOGICAL SURVEY CIRC. 68H, 1973,

  • Deposit

    99 PP.

  • Deposit

    PEOPLES, J.W., A.L. HOWLAND, W.R. JONES, AND D. FLINT.

  • Deposit

    GEOLOGIC MAP, SECTIONS, AND UNDERGROUND WORKINGS OF THE

  • Deposit

    MOUNTAIN VIEW LAKE AREA, STILLWATER COUNTY, MONTANA,

  • Deposit

    U.S. GEOLOGICAL SURVEY OPEN FILE RPT., 1954, 2 MAPS, 8 SECTIONS

  • Deposit

    WIMMLER, N.L. INVESTIGATION OF CHROMITE DEPOSITS OF THE

  • Deposit

    STILLWATER COMPLEX, STILLWATER AND SWEETGRASS COUNTIES,

  • Deposit

    MONTANA, U.S. BUR. OF MINES R.I. 4368, 1948, 41 PP.

  • Deposit

    MCHUGH, E., 1994, MLA REPORT IN PREPARATION.

General comments

Subject category Comment text
Deposit GSC ID # ISM0046 USGS LIST AS OF JUNE 95. MO60101 NOT ON THIS LIST. LAT/LONG ON 06/95 USGS LIST IS N452200/W1094900. ALSO LISTED AS ISMI-CR056 ON USGS LIST, 06/95.

Reporter information

Type Date Name Affiliation Comment
Reporter 27-JUN-95 Spear, James M. U.S. Bureau of Mines