Cinnabar Creek placer

Prospect, Undetermined

Commodities and mineralogy

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

Geographic location

Quadrangle map, 1:250,000-scale TA
Quadrangle map, 1:63,360-scale D-8
Latitude 60.795
Longitude -158.864
Nearby scientific data Find additional scientific data near this location
Location and accuracy This placer cinnabar prospect is located in a northeast headwater tributary of Cinnabar Creek locally called Cinnabar Run and Cinnabar Gulch. The placer is about 1 mile long from its origin as a residual deposit over the Cinnabar Creek lode deposit (TA001) at the head of Cinnabar Gulch. The map site is the approximate midpoint of the placer on Cinnabar Run, in the SW1/4 of section 12, T 8 N, R 55 W, of the Seward Meridian. It is 0.5 mile north-northeast of the north end ot the Cinnabar Creek airstrip. This prospect is accurately located. It is locality 9 of Cobb (1972 [MF 384]; 1976 [OF 76-606]).

Geologic setting

Geologic description

Russell Schaeffer and Harvey Winchell found this placer cinnabar deposit in 1941, the year they staked placer claims on Cinnabar Creek, Cinnabar Run, and Cinnabar Gulch (Rutledge, 1950, p. 3). The deposit was subsequently explored by dozer cuts in its upper part and by many test pits. The alluvium in the drainage is only about 100 to 150 feet wide, and in places the pay streak is only about 25 feet wide. The pay streak is at least 3,100 feet long. It is covered by up to 18 feet of colluvium/alluvium in Cinnabar Gulch and by about 7 feet of alluvial gravel along Cinnabar Run and Cinnabar Creek. Although Cady and others (1955) reported that the pay streak was only about 2 to 6 inches thick, test pits indicate that the minable section commonly is 5 feet thick and in the upstream part of the deposit, up to 14 feet thick (Rutledge, 1950, fig. 7). The placer contains many coarse nuggets to fist size of finely crystalline cinnabar, and many nuggets of cinnabar intergrown with quartz, stibnite, and breccia fragments of siltstone. The nuggets are angular in Cinnabar Gulch and well-rounded downstream along Cinnabar Run. Data from 14 test pits, mostly along Cinnabar Run, show that the pay streak is continuous, although locally narrow, and contains 0.21 to 0.84 percent Hg over mining sections varying from 5 to 14 feet thick (Rutledge, 1950, fig. 7). A few nuggets were obtained from a remnant bench placer deposit 40 feet above the Cinnabar Run flood plain.
Geologic map unit (-158.866275919976, 60.794278625449)
Mineral deposit model Alluvial placer cinnabar
Age of mineralization Quaternary.

Production and reserves

Workings or exploration Many test pits and some dozer trenches, including one 390 feet long and up to 18 feet deep excavated by the U.S. Bureau of Mines, have explored this placer deposit.
Indication of production Undetermined
Reserve estimates It is possible that much of this deposit is still in place. If the deposit is 4,000 feet long, 25 feet wide, 5 feet thick, and averages 0.4 pounds of Hg per cubic yard, then the contained resource is about 2,200 pouinds of mercury.
Production notes Production from this placer deposit has not been reported; it is not clear if mining has taken place (Sainsbury and MacKevett, 1965, p. 42).

References