Unnamed (beside Cobblestone Creek)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Mn

Geographic location

Quadrangle map, 1:250,000-scale CL
Quadrangle map, 1:63,360-scale C-1
Latitude 68.5097
Longitude -150.3917
Nearby scientific data Find additional scientific data near this location
Location and accuracy The occurrence is in bluffs and outcrops on the west side of Cobblestone Creek at an elevation of about 2300 feet. It is about 15.7 kilometers south of Arc Mountain near the northwest corner of section 12, T. 11 S., R. 7 E.

Geologic setting

Geologic description

Shale and silty mudstone of the Lower Cretaceous Torok Formation are exposed along Cobblestone Creek in bluffs and outcrops just west of the creek. Greenish-brown mudstone and shale locally display intense manganese staining (Kurtak and others, 1995). Four samples across a zone 6.5 meters thick contained 2.4 to 11.7 percent manganese. Another sample across a zone 4.5 meters wide contained 5.5 percent manganese. A sample examined by the U.S. Bureau of Mines contained 61.9 percent iron, 15.2 percent silica, 7.4 percent aluminum, 5.8 percent calcium, 4.8 percent manganese, and 4.0 percent phosphorus (Barnwell and others, 1989). The main mineral in the sample is siderite; no specific manganese mineral was identified. Similar manganese-stained rocks occur along a northeast-trending zone about 2.3 kilometers long.
Geologic map unit (-150.394505583656, 68.5093003923806)
Mineral deposit model Sedimentary manganese.
Age of mineralization Early Cretaceous host rock.

Production and reserves

Workings or exploration Only sampling by government agencies.
Indication of production None

Additional comments

MAS No. 0020220011.