Prospect, Undetermined

Commodities and mineralogy

Main commodities Ag; Cu; Zn
Other commodities Au
Ore minerals chalcopyrite; pyrite; pyrrhotite; sphalerite

Geographic location

Quadrangle map, 1:250,000-scale CR
Quadrangle map, 1:63,360-scale A-4
Latitude 55.08888
Longitude -133.16951
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Yellowstone prospect is at an elevation of about 2,200 feet, about 0.6 mile north of peak 2750 on Thunder Mountain and about 0.3 mile southwest of the center of section 23, T. 78 S., R. 81 E.

Geologic setting

Geologic description

The Yellowstone prospect was located prior to 1910 (Knopf, 1910, 1911; Berg and Cobb, 1967) but little work has been done on it since. When examined by D. J. Grybeck (unpublished field notes, 1984) and by Maas and others (1991, 1995), the workings were several small, prominent, prospect pits and one short adit. The deposit consists of several small pods of hornfels and skarn in limestone interbedded with chert and argillite. The limestone is cut by several prominent diabase dikes that probably are not related to the mineralization. The hornfels and skarn on the dumps contain abundant chalcopyrite and pyrrhotite; pyrite is also present, and on one dump, sphalerite. Selected samples (D.J. Grybeck, unpublished analyses, 1984) contained up to 30 parts per million (ppm) silver, 2 percent copper, and 1,000 ppm zinc. Samples collected by Maas and others (1991) contained up to 7.89 percent zinc, 1.8 percent copper, and 11 ppm silver. Gold values were barely above the detection level of 5 parts per billion. The prospect is in a thrust plate of Silurian Heceta Limestone that overlies sedimentary rocks of the Descon Formation of Silurian and Devonian age (Eberlein and others, 1983; Brew, 1996).
Geologic map unit (-133.171155396709, 55.0885253354966)
Mineral deposit model Ag-Cu-Zn skarn (Cox and Singer, 1986; models 18b or 18c).
Mineral deposit model number 18b, 18c
Age of mineralization Silurian or younger.

Production and reserves

Workings or exploration The only workings are several small prospect pits and a short adit that date from before 1910.
Indication of production None