Prospect, Undetermined

Commodities and mineralogy

Main commodities Hg
Other commodities Sb
Ore minerals cinnabar; marcasite; pyrite; stibnite
Gangue minerals limonite; quartz

Geographic location

Quadrangle map, 1:250,000-scale TA
Quadrangle map, 1:63,360-scale D-8
Latitude 60.79
Longitude -158.85
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Schaeffer prospect is located on the ridge north of Cinnabar Creek (TA002). The map site is at an elevation of about 1,550 feet, in the NE1/4 of section 13, T 8 N, R 55 W, of the Seward Meridian. It is 0.8 mile southeast of Cinnabar Gulch (TA001). This is locality 2 of Cobb 1972 [MF 384]; 1976 [OF 76-606]).

Geologic setting

Geologic description

This prospect was discovered by Russell Schaeffer in 1958 and subsequently explored by a few shallow, hand-dug (?) trenches (Sainsbury and MacKevett, 1965, p. 40). The deposit is cinnabar- and stibnite-bearing, quartz-cemented breccia of Triassic chert and siltstone. The breccia is irregular in thickness and trends N 20 W, parallel to bedding in the host rocks. Cinnabar and stibnite are irregularly disseminated in the breccia and locally replace quartz and breccia fragments; the owner reported to Sainsbury that fossils replaced by cinnabar had been found at this prospect. The richest ore contains 1 to 2 percent cinnabar. The breccia is limonite-stained, but pyrite and/or marcasite has only been observed in the altered siltstone.
Geologic map unit (-158.85227558924, 60.7892786491513)
Mineral deposit model Cinnabar and stibnite disseminated in quartz-cemented breccia (Hot-spring Hg?; Cox and Singer, 1986; model 27a?).
Mineral deposit model number 27a?
Age of mineralization Cretaceous or Tertiary. Inferred to be similar in age to other mercury deposits of southwest Alaska that postdate deposition of mid-Cretaceous clastic sedimentary rocks and intrusion of Upper Cretaceous or Tertiary igneous rocks.
Alteration of deposit Silicification and limonite-staining.

Production and reserves

Workings or exploration A few shallow trenches were dug on this prospect.
Indication of production None