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Colorado Creek Mine, Innoko District, Yukon-Koyukuk Borough, Alaska, USA

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Latitude & Longitude (WGS84): 63° 36' 46'' North , 155° 59' 49'' West
Latitude & Longitude (decimal): 63.6127777778, -155.996944444

See Neirod-East (MD020), Montana Saddle (MD018), and Montana Creek (MD015) prospects.
Location: This placer mine is situated in Colorado Creek basin above the junction of Creston Creek; the center of the placer is at an elevation of 550 feet (167 m) in Section 5, T. 22 S., R. 15 E., of the Kateel River Meridian. The site is accurately located; the reporter worked at the site in 1996.
Geology: The Colorado Creek gold-polymetallic placer deposit in the Medfra quadrangle is a portion of a 6.5 mile (10.4 km) long auriferous placer paystreak originating in the Cripple Creek Mountains. The payzone in the Medfra C-6 quadrangle comprises about 2.0 miles (3.2 km) or 30 percent of the total commercially exploited deposit. The auriferous gravels in the lower end average about 16 feet (5 m) thick and have an average width of 800 feet (243 m). The east limit of the paystreak gradually turns into an elevated ancestral bench overlain by up to 40 feet (12 m) of mixed eolian and colluvial deposits of Illinoin and Wisconsin age. The overburden contains well preserved Pleistocene megafauna which has been excavated by University of Alaska-Fairbanks Museum personnel (Thorson and Guthrie, 1982). The gravels in Colorado Creek paystreak contain abnormally high concentrations of boulders up to 3 feet (0.9 m) in diameter derived from the Cripple Creek Mountains. This, coupled with knowledge that the Cripple Creek Mountains were glaciated in Quaternary time, suggests a glaciofluvial outwash origin for the placer deposits (Bundtzen and others, 1997). Gold in Colorado Creek averages 873 fine with 121 silver. Anomalous mercury (up to 2.02 percent) was detected in some placer gold. An unusual group of rare heavy minerals were identified from mine concentrates, including traces of palladium, the niobium-uranium-yttrium mineral samarskite, the vanadium mineral coulsonite, and the silver sulfosalt xanthoconite (Bundtzen and others, 1987). In addition, an abnormally high concentration of garnet-magnetite-tactie cobbles have been recovered in cleanups, presumably derived from mineralization at the Neirod-East prospect (MD007).
Workings: Almost all past production has been from surface workings. Prior to 1915, some shafts were driven near the junction of Colorado Creek with Creston Creek. Beginning in 1930, hydraulic mine operations predominated, and from the late 1930s to the present, dragline-bulldozer have predominated. Hydraulic boom-dam methods proved to be very successful in previous years. From 1946 to 1948, the Goodnews Bay Mining Company conducted an extensive churn drilling program on Colorado Creek in anticipation of proving up a reserve that could be mined by a bucket line dredge. The company terminated the project and judged it was not suitable for a dredge. (John Fullerton, 1998). In recent years, the payzone has averaged about 0.015 ounces gold per cubic yard of pay (Ron Rosander, written communication, 1997).
Age: Middle Pleistocene, based on isotopic dates from overburden and geological inference (Bundtzen and others, 1997; Thorson and Guthrie, 1982).
Production: The first reported gold production from Colorado Creek occurred in 1913, when O. A. Olsen mined from a shaft near Creston Creek on a small scale (Bundtzen and others, 1997). After World War I, production was intermittent until 1928, when Sid Paulsen initiated a hydraulic mining venture. Dragline-bulldozer equipment was introduced in 1937. Mining continued on a small scale during World War II. From 1949 to 1958, Fullerton Brothers Mining Inc. and Strandberg and Sons Mining Inc. conducted large scale dragline-bulldozer operations in two locations on the creek. The Fullertons worked on the lower end mainly in the Medfra quadrangle. Mine activities ceased by 1960s. Beginning in 1974, Rosander Mining Company acquired most of the claims in the Colorado Creek basin and initiated medium scale dragline-bulldozer operations, which continues to the present day. Based on researching past mining records, Bundtzen and others (1997) estimate that approximately 110,000 ounces (3,421 kg) of gold and 12,500 ounces (388 kg) of silver were produced in Colorado Creek from 1913 to 1997. About 30 percent of this total came from the portion of the deposit within the Medfra C-6 quadrangle.

Commodities (Major) - Ag, Au; (Minor) - Hg, Pd, Sb, U
Development Status: Yes; medium
Deposit Model: Placer Au-PGE deposits (Cox and Singer, 1986; model no. 39a)

Mineral List

8 valid minerals.

Regional Geology

This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.

Click on geological units on the map for more information. Click here to view full-screen map on

Mesozoic - Paleozoic
66 - 541 Ma
Igneous: extrusive; Extrusive: undivided

Age: Phanerozoic (66 - 541 Ma)

Description: Interior western Alaska, Yukon-Koyukuk Basin

Comments: Sedimentary basin; Wilson & Hults, unpublished compilation, 2007-08

Lithology: Volcanic rocks; lava flows, pyroclastic debris

Reference: J.C. Harrison, M.R. St-Onge, O.V. Petrov, S.I. Strelnikov, B.G. Lopatin, F.H. Wilson, S. Tella, D. Paul, T. Lynds, S.P. Shokalsky, C.K. Hults, S. Bergman, H.F. Jepsen, and A. Solli. Geological map of the Arctic. doi:10.4095/287868. Geological Survey of Canada Map 2159A. [2]

541 - 2500 Ma
Schist of the Telsitna River

Age: Proterozoic (541 - 2500 Ma)

Description: Chiefly pelitic and quartzose metasedimentary rocks of greenschist metamorphic facies. Micaeous quartzite and quartz-chlorite schist grade into quartz-muscovite-biotite-garnet schist. Subordinate calc schist and marble. Unit locally includes small bodies of greenstone and greenschist metabasite, granitic gneiss, and metamorphosed quartz porphyry. North-central Medfra quadrangle and southeast Ruby quadrangle

Lithology: Metamorphic

Reference: Wilson, F.H., Hults, C.P., Mull, C.G, and Karl, S.M. (compilers). Geologic map of Alaska. doi: 10.3133/sim3340. U.S. Geological Survey Scientific Investigations Map 3340, pamphlet 196. [21]

Data and map coding provided by, used under Creative Commons Attribution 4.0 License

This page contains all mineral locality references listed on This does not claim to be a complete list. If you know of more minerals from this site, please register so you can add to our database. This locality information is for reference purposes only. You should never attempt to visit any sites listed in without first ensuring that you have the permission of the land and/or mineral rights holders for access and that you are aware of all safety precautions necessary.


Bundtzen, T.K., Pinney, D.S., and Laird, G.M., 1997, Preliminary geologic map and descriptive data tables from the Ophir C-1 and western Medfra C-6 quadrangles, Alaska: Alaska Division of Geological and Geophysical Surveys Public Data File Report 97-46, 10 p., 1 sheet, scale 1:63,360. Mertie, J.B., Jr., 1936, Mineral deposits of the Ruby-Kuskokwim region, Alaska: U.S. Geological Survey Bulletin 864-C, p. 115-245. Patton, W.W. Jr., Moll, E.J., Dutro, J.T., Jr., Silberman, M.L., and Chapman, R.M., 1980, Preliminary geologic map of the Medfra quadrangle, Alaska: U.S. Geological Survey Open-File Report 80-811, one sheet at 1:250,000 scale. Thorson, R. M., and Guthrie, R.D., 1982, Stratigraphy of the Colorado Creek Mammoth locality, Alaska: Quaternary Research, vol. 37, no. 2, p. 214-278.

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