Colorado Creek

Mines, Active

Commodities and mineralogy

Main commodities Au
Other commodities Ag
Ore minerals coulsonite; gold; ilmenite; magnetite; powellite; samarskite; scheelite; stibnite; xanthoconite

Geographic location

Quadrangle map, 1:250,000-scale OP
Quadrangle map, 1:63,360-scale C-1
Latitude 63.5724
Longitude -156.0078
Nearby scientific data Find additional scientific data near this location
Location and accuracy Colorado Creek is a large, generally northwest-flowing tributary to Hunch Creek. Tailings are shown on the U.S. G. S. Ophir C-1 topographic map (1954) for approximately 2 miles along Colorado Creek; the coordinates correspond to the approximate midpoint of these tailings, which is in sec. 20, T. 22 S., R. 15 E., Kateel River Meridian. Colorado Creek also flows in the Medfra C-6 quadrangle; see also MD014. Colorado Creek is locality 9 of Cobb (1972 [MF 367]). This location is accurate.

Geologic setting

Geologic description

The rocks in the vicinity of Colorado Creek are Cretaceous sandstone and conglomerate of the Kuskokwim group and altered volcanic rocks (Bundtzen and others, 1987). The gravel in the creek consists primarily of granitic rocks and chert (Mertie, 1936). The gravel is about 8 feet thick and buried under 10-20 feet of muck (Eakin, 1914; Mertie, 1936).
A 6.5-mile-long pay streak extends along Colorado Creek from the Cripple Creek Mountains. This pay streak crosses into the Medfra C-6 quadrangle for approximately 2 miles and then returns to the Ophir quadrangle. Placer gold was recovered during large, non-float operations that also mined several feet of bedrock (Mertie, 1936; Cobb, 1973 [B 1374]). The fineness of the +10 mesh gold in Colorado Creek is 909.6, with 82.8 parts silver, and 2.57 parts impurities. The -8 to +14 mesh gold is 900.2 fine, with 91.8 parts Ag, and 8.15 parts impurities (Bundtzen and others, 1987). Heavy minerals found in concentrates from the Rosander Mining Co. placers include magnetite, ilmenite, coulsonite, anthophyllite, samarskite, powellite, and xanthoconite. An estimated 50% of the concentrate is magnetite; some platinum is reported in gold bullion (Bundtzen and others, 1987). Roehm (1937) reports the presence of scheelite and stibnite at Colorado Creek. The gold at Colorado Creek may be derived from Cretaceous or Tertiary meta-aluminous, alkali-calcic to quartz-alkalic monzonite plutons that are located nearby (Bundtzen and others, 1987), with local contributions from quartz-stibnite veins (see OP032), and mineralized fault zones and epithermal systems (see OP031).
Mining along Colorado Creek began in 1913 (Eakin, 1913) and continues to the present (2001) . Colorado Creek has consistently been one of the largest placer mines in the area and has been active nearly continuously with documentation of mining in 1913, 1915, 1924, 1930, 1935, 1937, 1939, 1940, 1950, and from 1979 to the present (Eakin, 1913; Mertie and Harrington, 1916; Smith, 1933; Smith, 1937; Roehm, 1937; Smith, 1941; Smith, 1942; Bundtzen and others, 1992). Both creek and bench placers of Colorado Creek have been mined (Cobb, 1973 [B 1374]). A conservative estimate of the total production for Colorado Creek is 110,000 ounces of gold and 4,644 ounces of silver (Bundtzen, 1999).
Also see OP005 and OP031-033.
Geologic map unit (-156.010177816084, 63.5717893114233)
Mineral deposit model Placer Au (Cox and Singer, 1986; model 39a)
Mineral deposit model number 39a
Age of mineralization The Colorado Creek placer deposit is middle Pleistocene, based on isotopic dates from overburden and geological inference (Bundtzen and others, 1987; Thorson and Guthrie, 1992). The source of the placer gold may be the Cretaceous or Tertiary meta-aluminous, alkali-calcic to quartz-alkalic monzonite plutons that are located nearby (Bundtzen and others, 1987).

Production and reserves

Workings or exploration Mining began in 1913 and continues to the present 2001). Colorado Creek has consistently been one of the largest placer mines in the district. Mining at Colorado Creek may be nearly continuous. Reports exist of mining in 1913, 1915, 1924, 1930, 1935, 1937, 1939, 1940, 1950, and from 1979 to the present (Eakin, 1913; Mertie and Harrington, 1916; Smith, 1933; Smith, 1937; Roehm, 1937; Smith, 1941; Smith, 1942; Bundtzen and others, 1992). Both creek and bench placers of Colorado Creek have been mined (Cobb, 1973 [B 1374]). The first mechanized mining along Colorado Creek was prior to World War II, when Sidney Paulson began mining with a dragline. The Fullerton brothers (Colorado Creek Mining Co.) mined Colorado Creek from about 1950 until about 1957 (Ron Rosander, oral communication, 2001). In 1983, a woolly mammoth skeleton was found at Colorado Creek; Rosander Mining Co. donated the skeleton to the University of Alaska Museum. Rosander Mining Co. has worked the ancestral channels of Colorado Creek's right bench since 1979 (Bundtzen and others, 1992). Additional exploration of the Colorado Creek area, including soil sampling, took place during the summer of 1998.
Indication of production Yes; medium
Production notes A conservative estimate of production from Colorado Creek is 110,000 ounces of gold (Bundtzen, 1999).

Additional comments

For more information on Colorado Creek, contact the current claim owner, Ron Rosander, in McGrath, AK.

References

MRDS Number A010750; A015007

References

Thorson, R.M., and Guthrie, R.D., 1992, Stratigraphy of the Colorado Creek mammoth locality, Alaska: Quaternary Research, v. 37, no. 2, p. 214-228.
Reporters C.E. Cameron
Last report date 8/7/2001