Unnamed (East Fork of Glen Creek)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Rhodonite
Other commodities Mn
Ore minerals pyrolusite; rhodochrosite; rhodonite

Geographic location

Quadrangle map, 1:250,000-scale MM
Quadrangle map, 1:63,360-scale C-2
Latitude 63.564
Longitude -150.7306
Nearby scientific data Find additional scientific data near this location
Location and accuracy This is an inferred location for a proximate bedrock source of rhodonite boulders that have long been known to occur in Glen Creek (MM108). The location of the boulders is in the East Fork of Glen Creek about a half-mile above its confluence with the West Fork. It is somewhat upstream of occurrence 76 of Thornsberry, McKee, and Salisbury (1984), cited as a rhodonite boulder locality, but seems to agree more closely with their text description of the locality.

Geologic setting

Geologic description

Manganiferous boulders have long been known in Glen Creek. The boulders contain rhodonite and rhodochrosite, and are stained with a black oxide, probably pyrolusite. An early-reported location of the boulders is on so called Claim No. 9, where black-stained pebbles and small boulders of rhodonite accompanied placer gold and galena (Capps, 1919, p. 84). It is not certain whether this claim is in the East Fork or in Glen Creek below the junction of the two forks. Rhodonite on Glen Creek was also reported by Wells (1933, p. 355-356; p. 372); and Bundtzen, Smith, and Tosdal (1976, p. 9) reported that some of the rhodonite in Glen Creek is of gem quality. The rhodonite is a gem mineral, not an ore of manganese.
The country rock near the boulder locality consists partly of marble of the Spruce Creek sequence, a possible host for replacement(?) deposits of manganese minerals.
Geologic map unit (-150.732882522721, 63.5634986469422)
Age of mineralization The boulder deposit is Holocene.
Alteration of deposit Oxidation of manganese mineral.

Production and reserves

Workings or exploration The manganiferous boulders may have been discovered in 1916, when they were reported in sluice box concentrate on Claim No. 9 (Capps, 1919). They were also noted in 1931 (Wells, 1933), and in recent mining operations (Bundtzen, Smith, and Tosdal, 1976; Thornsberry, McKee, and Salisbury, 1984).
Indication of production None
Production notes Small amounts of the rhodonite have probably been sold as gem material.

Additional comments

The boulder deposits and their presumed bedrock source are in Denali National Park and Preserve.