Stillwater Anorthosite

The Stillwater Anorthosite is a aluminum mine located in Sweet Grass county, Montana at an elevation of 8,990 feet.

About the MRDS Data:

All mine locations were obtained from the USGS Mineral Resources Data System. The locations and other information in this database have not been verified for accuracy. It should be assumed that all mines are on private property.

Mine Info

Satelite View

MRDS mine locations are often very general, and in some cases are incorrect. Some mine remains have been covered or removed by modern industrial activity or by development of things like housing. The satellite view offers a quick glimpse as to whether the MRDS location corresponds to visible mine remains.

Site Name

Primary: Stillwater Anorthosite
Secondary: Stillwater Complex

Commodity

Primary: Aluminum
Tertiary: Calcium
Tertiary: Sodium
Tertiary: Silica
Tertiary: Magnesite
Tertiary: Iron

Location

State: Montana
County: Sweet Grass
District: Stillwater

Land Status

Land ownership: National Forest
Note: the land ownership field only identifies whether the area the mine is in is generally on public lands like Forest Service or BLM land, or if it is in an area that is generally private property. It does not definitively identify property status, nor does it indicate claim status or whether an area is open to prospecting. Always respect private property.

Holdings

Type: Patented
Type: Located Claim
Type: Federal Lease

Workings

Type: Surface

Ownership

Owner Name: National Forest
Home Office: Dist Of Columbia
Info Year: 1977

Owner Name: Johns-Manville Products Corp.
Home Office: Colorado
Info Year: 1977

Owner Name: Cyprus Mines
Home Office: California
Info Year: 1977

Owner Name: Amax, Inc.
Home Office: Connecticut
Info Year: 1977

Owner Name: Anaconda Co.
Home Office: New York
Info Year: 1977

Production

Not available

Deposit

Record Type: Site
Operation Category: Prospect
Operation Type: Surface
Mining Method: Unknown
Discovery Year: 1916
Years of Production:
Organization:
Significant: N

Physiography

General Physiographic Area: Rocky Mountain System
Physiographic Province: Middle Rocky Mountains

Mineral Deposit Model

Not available

Orebody

Not available

Structure

Not available

Alterations

Not available

Rocks

Not available

Analytical Data

Not available

Materials

Unknown: Olivine
Unknown: Enstatite
Unknown: Bytownite

Comments

Comment (Reserve-Resource): MATRIX TONNAGE AND GRADE FIGURES WERE DETERMINED BY HUSTEAD OF GEORGIA TECH.

Comment (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.

References

Reference (Deposit): U.S. GEOLOGICAL SURVEY CIRCULAR 684, P. 6.

Reference (Deposit): U.S. BUREAU OF MINES IC 8335, P. 86-87, 1967.

Reference (Deposit): PP. 300-302.

Reference (Deposit): PETROLOGY; 2ND ED.. MCGRAW HILL BOOK CO., PUB., 1960,

Reference (Deposit): TURNER, F.J., AND J. VERHOOGEN. IGNEOUS AND METAMORPHIC

Reference (Deposit): ANORTHOSITE. BUMINES BULL. 577, 1959, 127 PP.

Reference (Deposit): OF EXPERIMENTAL PLANT FOR PRODUCING ALUMINA FROM

Reference (Deposit): R.C. MERRITT, M.R. HOWCROFT, AND M. HAYASHI. OPERATION

Reference (Deposit): ST. CLAIR, H.W., D.A. ELKINS, B.K. SHIBLER, W.M. MAHAN,

Reference (Deposit): MONTANA. U.S. GEOLOGICAL SURVEY BULL. 1071-W, 1960, PP. 281-340

Reference (Deposit): AND TECTONIC STRUCTURES OF THE STILLWATER COMPLEX,

Reference (Deposit): JONES, W.R., J.W. PEOPLES, AND A.L. HOWLAND. IGNEOUS

Reference (Deposit): V. 80, 1969, PP. 1599-1604.

Reference (Deposit): OF THE STILLWATER COMPLEX. GEOL. SOC. AMER. BULL.

Reference (Deposit): FENTON, M.D. AND G. FAURE. THE AGE OF IGNEOUS ROCKS

Reference (Deposit): SOC. AM. MEM. 80, 1960, 230 PP.

Reference (Deposit): HESS, H.H. STILLWATER IGNEOUS COMPLEX, MONTANA. GEOL.

Principal Gold Districts of Montana

In Montana, 54 mining districts have each have produced more than 10,000 ounces of gold. The largest producers are Butte, Helena, Marysville, and Virginia City, each having produced more than one million ounces. Twenty seven other districts are each credited with between 100,000 and one million ounces of gold production. Read more: Principal Gold Districts of Montana.