Unnamed (near 'Spruce Mountain')

Occurrences, Probably inactive

Commodities and mineralogy

Main commodities Ag; Au; Cu; Pb; Zn

Geographic location

Quadrangle map, 1:250,000-scale SD
Quadrangle map, 1:63,360-scale C-4
Latitude 57.58696
Longitude -133.26744
Nearby scientific data Find additional scientific data near this location
Location and accuracy These occurrences identified by Kimble and others (1984) are part of a large altered zone with metal values (1984). The occurrences are scattered along a zone about 5,000 feet long oriented north-northwest. The center of the area is about 0.4 mile north of hill 4330 which is locally called 'Spruce Mountain'. It is about 0.5 mile southwest of the center of section 29, T. 49 S., R. 76 E.

Geologic setting

Geologic description

These occurrences are part of a band of prospects and mineral occurrences (SD046-049) 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, this deposit is notably different from many of the prospects in the Windham Bay area in that the mineralization is stratiform.
This site is a narrow zone that trends north-northwest for about 5,000 feet. Numerous occurrences along the zone consist of weathered, limonite-stained bands parallel to the foliation of the muscovite schist (Kimble and others, 1984). There are no workings. Of the 18 samples collected by Kimble and others (1984) along the zone, four have notable metal values: 1) a 100-foot chip sample contained 5 parts per million (ppm) silver, 1,300 ppm lead, and 7,600 ppm zinc; 2) a 17-foot chip sample contained 3 ppm silver, 0.05 ppm gold, and 1,900 ppm zinc; 3) a 105-foot chip sample contained 3 ppm silver, 0.05 ppm gold, 390 ppm copper, 60 ppm lead, and 2,100 ppm zinc; and 4) a 50-foot chip sample contained 2 ppm silver, 170 ppm lead, and 1,000 ppm zinc.
Geologic map unit (-133.269144961077, 57.5866206685968)
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 The occurrences are in iron-stained schist with limonite.

Production and reserves

Indication of production None

Additional comments

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