Stillwater Anorthosite

Prospect in Sweet Grass county in Montana, United States with commodities Aluminum, Calcium, Iron, Magnesite, Silica, Sodium
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. Reserves and resources
  16. Workings at the site
  17. Links to other databases
  18. Bibliographic references
  19. General comments
  20. Reporter information

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)

Site location context

Political divisions (FIPS codes)

Sweet Grass(county)

Montana(state)

United States(country)

North America(continent)

Land(continent)

USGS map quadrangles

Picket Pin Mountain(quadrangle 1:24,000 scale)

Gardiner(quadrangle 1:100,000 scale)

Bozeman(quadrangle 1:250,000 scale)

Hydrologic units (watersheds)

Upper Yellowstone(hydrologic unit)

Upper Yellowstone(hydrologic accounting unit)

Upper Yellowstone(hydrologic subregion)

Missouri(hydrologic region)

Federal lands

Custer Gallatin 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 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 Critical 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

Economic information

Ore body information

  • Strike N70W
    Dip 75N
    Thickness 1200M
    Length 14500M
    Width 350M
    Area 4625HA
    Depth to top 0M
    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:75N
    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 about the deposit and operations

Operation type Surface
Development status Prospect
Commodity type Both
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 4100000000mt ore
    Total resources 8300000000mt ore
    Commodity Subtype Grade units Group Importance Year
    Silica SiO2 48.5 wt-pct Silica Trace 1967
    Magnesite MgO 0.4 wt-pct Magnesium Trace 1967
    Aluminum Al2O3 32.2 wt-pct Aluminum Major 1967
    Iron Fe2O3 0.5 wt-pct Iron 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

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

Beyond USGS

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

Operator history (post-MRDS)

MRDS records operators as of each record's last update (≤ 2019). Some of the operators listed here have since changed hands or dissolved:

Curated by qvyshift.com from publicly-reported M&A activity (SEC filings, press releases, USGS Mineral Yearbooks). Not authoritative — verify against primary sources before relying on it. The MSHA panel above is the current authoritative source for actively-permitted mines.