Iron Mountain-Chrome Group W

The Iron Mountain-Chrome Group W is a chromium mine located in Sweet Grass county, Montana at an elevation of 9,449 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: Iron Mountain-Chrome Group W
Secondary: Chrome Group

Commodity

Primary: Chromium
Secondary: PGE

Location

State: Montana
County: Sweet Grass
District: In Stillwater Complex

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

Not available

Workings

Not available

Ownership

Not available

Production

Not available

Deposit

Record Type: Site
Operation Category: Occurrence
Operation Type: Unknown
Discovery Year: 1940
Discovery Method: Ore-Mineral In Place
Years of Production:
Organization:
Significant: N
Deposit Size: S

Physiography

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

Mineral Deposit Model

Model Name: Bushveld Cr

Orebody

Form: MASSIVE BAND, DISSEMINATED

Structure

Type: R
Description: 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)

Type: L
Description: Cross-Faulting

Alterations

Not available

Rocks

Name: Harzburgite
Role: Host
Age Type: Host Rock
Age Young: Early Cretaceous

Name: Harzburgite
Role: Host
Age Type: Associated Rock Unit
Age Young: Neoarchean

Analytical Data

Analytical Data: TRENCHES YIELEDED 0.5-5 FT CHROMITE AT 3.33-39.57% CR2O3 (AVERAGE 2.65 FT AT 17.9% CR2O3). 1 SAMPLE OF CHROMITITE: 71 PPB PT, 270 PPB PD, 40 PPB RH.

Materials

Ore: Chromite
Gangue: Olivine
Gangue: Serpentine

Comments

Comment (Location): UNSURVEYED. LOCATED ON EAST SLOPE OF IRON MOUNTAIN. IN CUSTER NATIONAL FOREST

Comment (Workings): SHALLOW TEST PITS AND TRENCHES

Comment (Geology): AGE OF STILLWATER COMPLEX IS 2,705 +/- 4 MA BASED ON U-PB SYSTEMATICS ON ZIRCON-BADDELEYITE (PREMO AND OTHERS, 1990)

Comment (Deposit): CHROMITITE A AND G LAYERS ARE PRESENT. MAXIMUM GIVEN IS MASSIVE ORE; DISSEMINATED ORE IS 3.5 FT MAX.

References

Reference (Deposit): SCHAFER, P.A., 1937, CHROMITE DEPOSITS OF MONTANA: MONTANA BUREAU OF MINES AND GEOLOGY MEMOIR 18, P. 14-16.

Reference (Deposit): HOWLAND, A.L., 1955, CHROMITE DEPOSITS IN THE CENTRAL PART OF THE STILLWATER COMPLEX, SWEET GRASS COUNTY, MONTANA: U.S. GEOLOGICAL SURVEY BULLETIN 1015-D, P. 113-114.

Reference (Deposit): WIMMLER, N.L., 1948, INVESTIGATION OF CHROMITE DEPOSITS OF THE STILLWATER COMPLEX, STILLWATER AND SWEETGRASS COUNTIES, MONT.: U.S. BUREAU OF MINES REPORT OF INVESTIGATIONS 4368, P. 38-39.

Reference (Deposit): 1955 GEOLMAP HOWLAND, BULL. 1015-D, P. 11

Reference (Deposit): ZIENTEK, M.L., 1993, MINERAL RESOURCE APPRAISAL FOR LOCATABLE MINERALS: THE STILLWATER COMPLEX, IN HAMMARSTROM, J.M., ZIENTEK, M.L., AND ELLIOTT, J.E., EDS., MINERAL RESOURCE ASSESSMENT OF THE ABSAROKA-BEARTOOTH STUDY AREA, CUSTER AND GALLATIN NATIONAL FORESTS, MONTANA: U.S. GEOLOGICAL SURVEY OPEN-FILE REPORT 93-207, P. F1-F83.

Reference (Deposit): PREMO, W.R., HELZ, R.T., ZIENTEK, M.L., AND LANGSTON, R.B., 1990, U-PB AND SM-ND AGES FOR THE STILLWATER COMPLEX AND ITS ASSOCIATED SILLS AND DIKES, BEARTOOTH MOUNTAINS, MONTANA: IDENTIFICATION OF A PARENT MAGMA?: GEOLOGY, V. 18, P. 1065-1068.

Reference (Deposit): PAGE, N.J, RILEY, L.B., AND HAFFTY, JOSEPH, 1969, PLATINUM, PALLADIUM, AND RHODIUM ANALYSES OF ULTRAMAFIC AND MAFIC ROCKS FROM THE STILLWATER COMPLEX, MONTANA: U.S. GEOLOGICAL SURVEY CIRCULAR 624, P. 10.

Reference (Deposit): PAGE, N.J, RILEY, L.B., AND HAFFTY, JOSEPH, 1972, VERTICAL AND LATERAL VARIATION OF PLATINUM, PALLADIUM, AND RHODIUM IN THE STILLWATER COMPLEX, MONTANA: ECONOMIC GEOLOGY V. 67, P. 915.

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.