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Stillwater Anorthosite

Prospect in Sweet Grass county in Montana, United States with commodities Aluminum, Calcium, Iron, Magnesite, Silica, Sodium
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Geologic information

Identification information

Deposit ID 10221786
MAS/MILS ID 0300970002
Record type Site
Current site name Stillwater Anorthosite
Alternate or previous names Stillwater Complex

Geographic coordinates

Point of reference Ore Body
Geographic coordinates: -110.0727, 45.46162 (WGS84)
Elevation 2740
Location accuracy 10(meters)
(click for info)

Geographic areas

Country State County
United States Montana Sweet Grass

Public Land Survey System information

Meridian Township Range Section Fraction State
Montana Principal 004 S 013 E 25 Montana

Commodities

Commodity Importance
Aluminum Primary
Calcium Tertiary
Iron Tertiary
Magnesite Tertiary
Silica Tertiary
Sodium Tertiary

Materials information

Materials Type of material
Bytownite Unknown
Enstatite Unknown
Olivine Unknown

Nearby scientific data

Ore Body (1) -110.0727, 45.46162
ListMap

Ore body information

  • Strike N70W
    Dip 75N
    Thickness 1200M
    Depth to top 0M
    Width 350M
    Length 14500M
    Area 4625HA
    Field Value
    MAS Matrix # 1
    MAS Column # 1
    Type of Orebody #1 OTHER
    Shape of Orebody #1 TABULAR
    Primary mode of Origin MAGMATIC DIFFER
    Primary Ore Control IGNEOUS
    Secondary Ore Control FAULTING
    Strike And Dip N70W
    Minimum Depth to Top 0
    Avg. Thick. Unconsol. Mat. 0
    Min. Thick. Unconsol. Mat. 0
    Total Surface Area (HA) 4625
    Date of Last Modification 980519

Economic information

Economic information about the deposit and operations

Operation type Surface
Development status Prospect
Commodity type Both metallic and non-metallic
Significant No
Discovery year 1916

Mining district

District name Stillwater

Mineral rights holdings

Type of mineral rights Federal Lease
Type of mineral rights Located Claim
Type of mineral rights Patented

Land status

Ownership category National Forest

Ownership information

  • Type Owner
    Owner Anaconda Co.
    Home office New York
    Year 1977
  • Type Owner
    Owner Amax, Inc.
    Home office Connecticut
    Year 1977
  • Type Owner
    Owner Cyprus Mines
    Home office California
    Year 1977
  • Type Owner
    Owner Johns-Manville Products Corp.
    Home office Colorado
    Year 1977
  • Type Owner
    Owner National Forest
    Home office Dist Of Columbia
    Year 1977

Reserves and resources

  • Type In-situ
    Estimate year 1967
    Inferred 4,100,000,000mt ore
    Total resources 8,300,000,000mt ore
    Commodity Subtype Grade units Group Importance Year
    Aluminum Al2O3 32.2 wt-pct Aluminum Major 1967
    Silica SiO2 48.5 wt-pct Silica Trace 1967
    Iron Fe2O3 0.5 wt-pct Iron Trace 1967
    Magnesite MgO 0.4 wt-pct Magnesium Trace 1967

Comments on the reserve resource information

  • MATRIX TONNAGE AND GRADE FIGURES WERE DETERMINED BY HUSTEAD OF GEORGIA TECH.

Workings at the site

  • Type of workings Surface
    Area 4625HA
    Field Value
    MAS Development Schedule # 1
    Mining Record # 1
    Status of Mining Method PROPOSED
    Mining Method BENCH (BERM)
    Swell Factor .65
    Avg. Overburden Thickness 0
    Primary Material Cover SAND, GRAVEL
    Hardness of Ore HARD ROCKS
    Avg. Bench Height (meters) 15
    Max. Pit Slope (degrees) 45
    Capacity 5428
    Capacity Units MT ORE/DAY
    Unit Production Cost 2.52
    Units of Production $/MT ORE
    Operating Days per Year 250
    Operating Shifts per Day 2
    Year of Information 1979

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
U.S. Bureau of Mines Minerals Availability System MAS 0300970002

Bibliographic references

  • Deposit

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

  • Deposit

    SOC. AM. MEM. 80, 1960, 230 PP.

  • Deposit

    FENTON, M.D. AND G. FAURE. THE AGE OF IGNEOUS ROCKS

  • Deposit

    OF THE STILLWATER COMPLEX. GEOL. SOC. AMER. BULL.

  • Deposit

    V. 80, 1969, PP. 1599-1604.

  • Deposit

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

  • Deposit

    AND TECTONIC STRUCTURES OF THE STILLWATER COMPLEX,

  • Deposit

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

  • Deposit

    ST. CLAIR, H.W., D.A. ELKINS, B.K. SHIBLER, W.M. MAHAN,

  • Deposit

    R.C. MERRITT, M.R. HOWCROFT, AND M. HAYASHI. OPERATION

  • Deposit

    OF EXPERIMENTAL PLANT FOR PRODUCING ALUMINA FROM

  • Deposit

    ANORTHOSITE. BUMINES BULL. 577, 1959, 127 PP.

  • Deposit

    TURNER, F.J., AND J. VERHOOGEN. IGNEOUS AND METAMORPHIC

  • Deposit

    PETROLOGY; 2ND ED.. MCGRAW HILL BOOK CO., PUB., 1960,

  • Deposit

    PP. 300-302.

  • Deposit

    U.S. BUREAU OF MINES IC 8335, P. 86-87, 1967.

  • Deposit

    U.S. GEOLOGICAL SURVEY CIRCULAR 684, P. 6.

General comments

Subject category Comment text
Deposit NOTE: DEPOSIT EXTENDS INTO ADJACENT STILLWATER COUNTY. THE BULK OF THE DEPOSIT IS IN SWEET GRASS COUNTY. THE COST INFORMATION CONTAINED IN THIS FILE IS INADEQUATE AND AND WILL REMAIN SO UNTIL ANORTHOSITE DEPOSITS CAN BE EVALUATED FURTHER. THERE ARE TWO SETS OF COSTS; ORIGINAL 1975 COSTS, AND COMPLETELY RECOSTED 1979 COSTS. ALL COSTS ARE ASSUMED TO BE MIDYEAR. DEPOSIT LIFE IS 2947 YEARS AT H PRODUCTION RATE OF 1,357,000 TONNES PER YEAR. THE MILL CAPACITY CAN BE INCREASED TO SHORTEN THE LIFE, OR OTHER MILLS CAN BE ADDED SUBSEQUENTLY OR CONCURRENTLY. THERE IS ENOUGH MATERIAL TO SUPPLY 117 SUCH PLANTS FOR 25 YEARS AND ONE PLANT FOR 22 YEARS. STRATIFORM ANORTHOSITE BODIES 1400 FT THICK, 17 TO 26 MILES LONG.

Reporter information

Type Date Name Affiliation Comment
Reporter 19-MAY-98 McHugh, Edward L. U.S. Bureau of Mines