Unnamed (southwest of 'Spruce Mountain')

Occurrence, Inactive

Commodities and mineralogy

Main commodities Ag; Au; Cu; Pb; Zn
Ore minerals chalcopyrite; galena; pyrite; pyrrhotite; sphalerite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale SD
Quadrangle map, 1:63,360-scale C-4
Latitude 57.57607
Longitude -133.27437
Nearby scientific data Find additional scientific data near this location
Location and accuracy This site is an altered zone identified by Kimble and others (1984). It is about 0.4 mile southwest of hill 4330 which is locally called 'Spruce Mountain'. The altered zone is about 0.3 mile east-southeast of the center of section 31, T. 49 S, R. 76 E.

Geologic setting

Geologic description

These occurrences are part of a band of prospects and mineral occurrences (SR046-049) in what is often referred to as the Third Zone of Spencer (1906; Kimble and others, 1984). These are generally gold-quartz veins and veinlets in muscovite schist of Cretaceous age (Brew and Grybeck, 1984). However, the deposits at this site are notably different from many of the prospects in the Windham Bay area, in that they are stratiform.
This site is a altered (weathered and iron-stained?) zone that strikes north-northwest for about 1,500 feet (Kimble and others, 1984). There were claims staked in the area in 1900 but there are no workings. The host rocks consist mainly of muscovite schist with white and yellow bands. The schist locally contains disseminated sulfides and occasional pods of quartz. The sulfides are mainly pyrite with minor pyrrhotite, sphalerite, chalcopyrite, and galena. The zone is about 120 feet thick at its south end and about 50 feet thick at its north end; it disappears under talus at both ends. Kimble and others (1984) collected 8 samples. The best was a 0.25-foot-thick channel sample that contained 150 parts per million (ppm) silver, 0.05 ppm gold, 2,100 ppm, copper, 21,000 ppm lead, and 4,800 ppm zinc. Most samples contained much less and the next best sample was a 50-foot chip sample that contained 10 ppm silver, 10 ppm gold, 60 ppm copper, 1,100 ppm lead, and 140 ppm zinc.
Geologic map unit (-133.276075264215, 57.575730051523)
Mineral deposit model Unclear; may be syngenetic or epigenetic and related to the numerous gold-quartz veins in the area.
Age of mineralization In schist of Cretaceous (metamorphic) age; the age of the protolith is unknown.
Alteration of deposit Schist that hosts the mineralization is altered but details not given; perhaps the alteration is mainly weathering of sulfides to limonite.

Production and reserves

Workings or exploration There were claims staked in the area in 1900 but there are no workings. Sampling by government geologists in the early 1980s (Kimble and others, 1984).
Indication of production None

Additional comments

The occurrence is in the Chuck River Wilderness Area which is closed to prospecting and mining.