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Stillwater Mine

Producer in Stillwater county in Montana, United States with commodities PGE, Palladium, Platinum, Gold, Rhodium, Copper, Nickel, Iridium, Osmium, Ruthenium
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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. Mineral occurrence model information
  9. Host and associated rocks
  10. Nearby scientific data
  11. Geologic structures
  12. Ore body information
  13. Controls for ore emplacement
  14. Economic information about the deposit and operations
  15. Mining district
  16. Mineral rights holdings
  17. Land status
  18. Ownership information
  19. Production statistics
  20. Reserves and resources
  21. Links to other databases
  22. Bibliographic references
  23. Reporter information

Geologic information

Identification information

Deposit ID 10270333
MRDS ID ISM0330
MAS/MILS ID 0300950032
Record type Site
Current site name Stillwater Mine
Alternate or previous names Stillwater Mining Co. Minn.Adit Prj, Minneapolis Adit Project, Johns-Manville Stillwater Platinum, Stillwater Platinum Project, Stillwater Pgm Resources, M Prospect
Included sites J-M Reef Deposit

Comments on the site identification

  • LISTED AS GSC ID # ISM0330 ON THE USGS JUNE 95 LIST UNDER THE NAME OF J-M REEF DEPOSIT. ALSO LISTED AS ISMI-PGE35. OTHER MAS SEQ# 0300970003. RELATED MAS SEQ# 0300970066: POSSIBLY TO 0300970031. THE STILLWATER PGM SMELTER IT MAY HAVE SOME RELATIONSHIP TO THIS PROPERTY. PREPRODUCTION YEARS BEGINNING IN 1982.

Geographic coordinates

Point of reference Main Entrance
Geographic coordinates: -109.87999, 45.38772 (WGS84)
Elevation 1600
Location accuracy 100(meters)

Site location context

Political divisions (FIPS codes)

Stillwater(county)

Montana(state)

United States(country)

North America(continent)

Land(continent)

USGS map quadrangles

Meyer Mountain(quadrangle 1:24,000 scale)

Red Lodge(quadrangle 1:100,000 scale)

Billings(quadrangle 1:250,000 scale)

Hydrologic units (watersheds)

Stillwater(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 Stillwater

Public Land Survey System information

Meridian Township Range Section Fraction State
Montana Principal 005 S 015 E 21 NE Montana

Commodities

Commodity Importance
PGE Critical Primary
Palladium Critical Primary
Platinum Critical Primary
Gold Secondary
Rhodium Critical Secondary
Copper Tertiary
Nickel Critical Tertiary
Iridium Critical Tertiary
Osmium Tertiary
Ruthenium Critical Tertiary

Materials information

Materials Type of material
Gold Ore
Palladium Ore
Platinum Ore
Chalcopyrite Ore
Pentlandite Ore
Pyrrhotite Ore
Mackinawite Ore
Pyrite Ore
Olivine Gangue
Plagioclase Gangue
Sphalerite Gangue
Galena Gangue
Apatite Gangue
Chlorite Gangue
Hornblende Gangue
Magnetite Gangue
Serpentine Gangue
Talc Gangue
Tremolite Gangue
Silver Unknown
Marcasite Unknown
Cubanite Unknown

Analytical data

Result HOST ROCKS CONTAIN 0.5-1.0% CHALCOPYRITE+PYRRHOTITE+PENTLANDITE WHICH CONTAIN SMALL AMOUNTS OF PLATINUM BEARING SULFIDES. ONE 5.5 KM SEGMENT OF REEF AVERAGES 22.3PPM PT+PD OVER 2.1 M WIDTH. PT:PD=1:3.

Mineral occurrence model information

Model code 4
USGS model code 2b
Deposit model name Merensky Reef PGE

Host and associated rocks

  • Host or associated Host
    Rock type Plutonic Rock > Mafic Intrusive Rock > Gabbro
    Rock unit name J-M Reef
  • Host or associated Host
    Rock type Plutonic Rock > Mafic Intrusive Rock > Gabbro > Troctolite
    Rock unit name J-M Reef
  • Host or associated Host
    Rock type Plutonic Rock > Mafic Intrusive Rock > Gabbro > Norite
    Rock unit name J-M Reef
  • Host or associated Host
    Rock type Plutonic Rock > Mafic Intrusive Rock > Anorthosite
    Rock unit name J-M Reef

Nearby scientific data

Main Entrance (1) -109.87999, 45.38772
ListMap

Economic information

Geologic structures

Type of structure Local
Structure name Folds
Type of structure Local
Structure name Faults
Type of structure Local
Structure name High-Angle Reverse Faults

Ore body information

  • Name J-M Reef
    General form Tabular, stratiform, disseminated
    Strike N80W-N60W
    Dip 55-70N, locally overturned
    Thickness 1.8M
    Length 4114M
    Width 701M
    Depth to top 350M
    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
    Degree of Wallrock Alter. NONE
    Type of Wallrock Alter. #1 UNKNOWN
    Strike And Dip N80W:55N
    Minimum Depth to Top 0
    Avg. Thick. Unconsol. Mat. 0
    Min. Thick. Unconsol. Mat. 0
    Total Surface Area (HA) 200
    Date of Last Modification 961007

Controls for ore emplacement

  • Magma Mixing

Comments on the geologic information

  • The Stillwater Complex Is Exposed Along The Northern Margin Of The Beartooth Uplift, One Of Several Laramide Basement-Cored Ranges That Make Up The Rocky Mountain Foreland Of South-Central Montana (Foose And Others, 1961: Kulik And Schmidt, 1988)
  • Tectonic Setting At Time Of Emplacement Of The Stillwater Complex Is Unknown. The Complex Was Emplaced Shortly After A Major Regional, Subduction-Related Magmatic Event That Culminated In Emplacement Of The 2.73-2.79 Ga Granitoid Suite In The Batholith Exposed In The Beartooth Uplift (Wooden And Others, 1991). However, There Is No Evidence That The Magmatism That Formed The Stillwater Complex Is Related To Convergent Margin Tectonics And Magmatism
  • Metals May Have Been Derived From Ultramafic Magma And Sulfur From Anorthositic Magma. If So, Sulfides Formed As Magmas Mixed
  • J-M REEF IS 400-450 M ABOVE BASE OF BANDED SERIES IN BASAL PART OF ANORTHOSITE I SUBZONE OF TROCTOLITE-ANORTHOSITE ZONE I. THIS COINCIDES WITH REAPPEARANCE OF OLIVINE IN CRYSTALLIZATION SEQUENCE. SULFIDES FORMED AS IMMISCIBLE LIQUID DROPS DURING EARLY STAGES OF REEF FORMATION ALONG WITH OLIVINE. STRUCTURES SIMILAR TO THE POTHOLE STRUCTURES IN THE MERENSKY REEF HAVE BEEN FOUND
  • THE J-M REEF IS 1-3 M THICK AND HAS BEEN TRACED FOR 40 KM. AGE OF STILLWATER COMPLEX IS 2,705 +/- 4 MA BASED ON U-PB SYSTEMATICS ON ZIRCON-BADDELEYITE (PREMO AND OTHERS, 1990)

Economic information about the deposit and operations

Operation type Underground
Development status Producer
Commodity type Metallic
Significant Yes
Discovery year 1971
Mining method Filled Stopes - Horiz Cut and Fill W/Waste Rock
Year of first production 1986
Plant type Beneficiation (Mill)
Plant subcategory Flotation
Milling method Flotation

Comments on exploration

  • THE J-M REEF DEPOSITS WERE DISCOVERED BY GEOCHEMICAL SURVEYS IN 1967, BUT THE PRESENCE OF SULFIDES WAS KNOWN IN THE 1930'S

Mining district

District name Stillwater

Mineral rights holdings

Type of mineral rights Located Claim
Type of mineral rights Patented

Land status

Ownership category National Forest

Ownership information

  • Type Owner-Operator
    Owner Stillwater Mining Co.
    ID 2401490
    Interest 100
    Home office Montana
    Year 1996
    First year 1994
  • Type Owner
    Owner Chevron Resources, Inc.
    ID 2401490
    Interest 50
    Year 1990
    First year 1979
    Last year 1994
  • Type Owner
    Owner Johns-Manville Products Corp.
    ID 2401490
    Interest 50
    Year 1990
    First year 1979
    Last year 1994
  • Type Operator
    Owner Stillwater PGM Resources
    Year 1998
    First year 1979
    Last year 1994

Production statistics

  • Year 1995
    Description Palladium Production 169000 Troy Ounces
    Importance Item Commodity Group Amount recovered Grade Recovery percentage
    Trace Palladium PGE 5256488.28g
  • Year 1995
    Description Platinum Production 51000 Troy Ounces
    Importance Item Commodity Group Amount recovered Grade Recovery percentage
    Trace Platinum PGE 1586277.53g

Comments on the production information

  • CONCENTRATE WOULD BE SHIPPED TO SUDBURY, ONTARIO, CANADA.
  • ONLY PRODUCER OF PGE AS PRIMARY COMMODITY IN THE CONTERMINOUS U.S. MINE REACHED MINING CAPACITY OF 1,000 TONS PER DAY IN 1990 FOR AN ANNUAL PRODUCTION RATE OF 50,000 OZ PT AND ABOUT 170,000 OZ PD (update- Boulder Creek on same unit is presently also mining PGE's)

Reserves and resources

  • Type In-situ
    Estimate year 1990
    Total resources 430920mt ore
    Commodity Subtype Grade units Group Importance Year
    PGE Pt 27.43 g/mt PGE Major 1990
  • Type In-situ
    Estimate year 1996
    Measured 767478mt ore
    Indicated 19718568mt ore
    Total resources 20486046mt ore
    Commodity Subtype Grade units Group Importance Year
    PGE PGE 27.61 g/mt PGE Major 1996
  • Type In-situ
    Estimate year 1997
    Demonstrated 24584706mt ore
    Total resources 24584706mt ore
    Commodity Subtype Grade units Group Importance Year
    PGE Pt 27.43 g/mt PGE Major 1997

Comments on the reserve resource information

  • PALLADIUM TO PLATINUM GRADE RATIO IS 3.5 TO 1.0 BEFORE PROCESSING AND LOSS OF 10%. THESE ARE EAST BOULDER AREA RESERVES.
  • PALLADIUM TO PLATINUM GRADE RATIO IS 3.5 TO 1.0 BEFORE PROCESSING AND LOSS OF 10%. PROVEN + PROBABLE ORE RESERVES, EAST BOULDER AREA, 12/31/95.
  • ALL PLATINUM GROUP ELEMENTS ARE PRESENT AND RECOVERABLE ASSAYS ARE NOT AVAILABLE FOR IR, OS, RU.

Comments on the workings information

  • Approximately early 1990;s 2 ADITS WITH CROSSCUTS, DRIFTS, RAISES. 4,570+ FT DIAMOND DRILL CORE.

Comments on other economic factors

  • BENEFICIATION STUDIES ARE CURRENTLY (4/81) IN PROGRESS BY RENO METALLURGY RECOVERY OF AU, NI, CU IS VERY LOW WHEN STUDIES ARE COMPLETED, RECOVERIES ARE EXPECTED TO IMPROVE.
  • ESTIMATED DILUTION IS 20%

Reference information

Bibliographic references

Reporter information

Type Date Name Affiliation Comment
Reporter 28-APR-97 Buckingham, David A. U.S. Bureau of Mines
Updater 04-JAN-11 Causey, J. Douglas U.S. Geological Survey Removed all workings records as they predated mining and were all USBM attempts to guess what would happen when mining began. Also fixed and added some info.
Reporter 01-SEP-91 Peterson, Jocelyn A. U.S. Geological Survey

Beyond USGS

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

Current status (per MSHA)

StatusActive since 05/15/1987
MSHA mine ID2401490
Mine name (MSHA)STILLWATER MINE
Current operatorStillwater Mining Company
Current controller (parent)Sibanye Stillwater Limited
Mine typeUnderground (Metal / non-metal)

MSHA cross-reference per the original MRDS record. Mine status and operator reflect MSHA's last published Mines export (February 2025); MSHA's public bulk feed has been unavailable since, so this may be out of date. See the Mine Data Retrieval System for current status.

Open MSHA's Mine Data Retrieval System for inspections, accidents, and violations for this mine.

External references

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