Benbow Chromium Mine
The Benbow Chromium Mine is near Nye, Montana. Historically the site has been associated with the Stillwater Mining District which is now part of the Custer National Forest. The site was first discovered before 1905. The Benbow Chromium Mine was closed at the time of data entry with no known plans to re-open. Production size when active was considered to be small. Mine operations consist of underground workings. There is one known shaft. Subsurface depth reaches a maximum of 183 meters (600 feet) and extends 14,261 meters (46,787 feet) in length. The ore mined is composed of chromite with waste material consisting primarily of olivine and serpentine. The ore body is massive and disseminated in form reaching 2,743 meters (9,000 feet) long and 2 meters (8 feet) thick. Associated rock in this area is quartz monzonite from the Neoarchean era (2.80 to 2.50 billion years ago) to the Lower Cretaceous epoch (145.00 to 100.50 million years ago). The Middle Rocky Mountains physiographic province of the Rocky Mountain System characterize the geomorphology of the surrounding area.
Site identification and general characteristics. Learn about USGS mines.
Additional textual information about a site or mine.
UNSURVEYED. LOCATION GIVEN IS FOR SHAFT SYMBOL ON MAP. DEPOSIT EXTENDS ACROSS LITTLE ROCKY CREEK. LOCATED NEAR EAST END OF STILLWATER COMPLEX. IN CUSTER NATIONAL FOREST.
Formal or informal mining district names.
PROPERTY WAS WORKED DURING WWI BUT NO SHIPMENTS WERE MADE; TOTAL$: 4; DEV$: 0. 701; ECON. YEAR: 1943; 1941-1943 FINANCED BY RECONSTRUCTION FINANCE CORP.; MILL. CAP : 182 ST.
Workings at the site.
ADITS, MORE THAN 100 TRENCHES, 2, 638 FEET DIAMOND DRILL HOLES.
Processes that concentrated or enriched the mineralization of the mine.
AGE OF STILLWATER COMPLEX IS 2, 705 +/-4 MA BASED ON U-LEAD SYSTEMATICS ON ZIRCON-BADDELEYITE (PREMO AND OTHERS, 1990 ); AGE OF HOST ROCKS: PRE CAMBRIAN; STILLWATER COMPLEX.
Characteristics of the ore body.
Geological materials at the site.
Geologic structural features affecting or characterizing the site or mine.
Tectonic setting in which the site or deposit is situated.
Physiographic area where the resource is found.
Mineralogical and chemical alteration at or near the site, which may help to indicate the geographic extent of the geological processes producing the mine.
Results of chemical or mineralogical analysis on materials at or near the site
Controls on emplacement of ore such as faults or other structural features.
JACKSON ESTIMATED TOTAL CHROMITE RESERVES OF STILLWATER COMPLEX TO BE 2, 520, 000 LONG TONS CR2O3.
RESOURCE POTENTIAL IS FOR AREA BETWEEN BENBOW AND MOUAT-SAMPSON AT A DEPTH OF LESS THAN 2, 000 FEET IDENTIFIED RESOURCES OF MOUAT-SAMPSON+BENBOW ARE 15 MILLION TONS AT 20-22% CR2O3.
Other deposits in the same region.
Benbow Chromium Mine
Benbow Nickel-Copper Nickel Prospect
Benbow Nickel-Copper Nickel Occurrence
Little Rocky Creek Nickel-Copper Copper Occurrence
Benbow Cr-Pt Chromium Occurrence
Nye Basin Cr-Pt Platinum Occurrence
Nye Basin Big Seven Prospect
Blitz Platinum Occurrence
Chrome Lake Cr-Pt Chromium Occurrence
Chrome Lake Nickel-Copper Copper Occurrence
* Mine bounds on map indicate the general area that a mine occupies. For an detailed map, refer to the overseeing BLM field office.
** The mine central point is based on an average of the mine's bounding box(es) and does not necessarily fall on the claim itself.
1 World-class significance is determined by total endowment of the contained commodity. This includes all past production and remaining reserves. Each commodity is considered separately and commodities cannot be combined to arrive at a significant size. The tonnage thresholds are from the mine model grade-tonnage studies. As of June 2008, many entries were classified as significant under less strict rules.
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THE AVERAGE THICKNESS OF THE DEPOSIT IS 4. 9 FEET AT 24. 5% CR2O3. G CHROMITITE ZONE HAS BEEN MINED. OVERLAPPING LENSES WITH DISSEMINATED ORE BETWEEN. THERE ARE MANY SMALL RIGHT-LATERAL OFFSETS IN THE MAIN CHROMITITE BAND ALONG NORTH TRENDING FAULTS. DEPOSIT IS CUT BY SEVERAL LARGE DIABASE DIKES. MASSIVE+DISSEMINATED ORE IS 50 FEET WIDE MAX.
THE LARGEST POTENTIAL RESOURCES OF CHROMIUM AND PGE IN THE U. S. ARE IN THE STILLWATER COMPLEX.; INFORMATION SOURCE: 1 PUB LIT.
RECORD W026522 HAS BEEN MERGED AND DELETED.