Slate Creek

Mine, Active?

Commodities and mineralogy

Main commodities Au
Other commodities Ag; Ba; Cu
Ore minerals barite; gold; native copper; native silver

Geographic location

Quadrangle map, 1:250,000-scale TN
Quadrangle map, 1:63,360-scale B-1
Latitude 65.36288
Longitude -150.16833
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Slate Creek placer mine is mainly in section 11, T. 6 N., R. 13 W., of the Fairbanks Meridian. The workings probably extend upstream for about a mile from a point about a mile above the junction of Minook Creek. The site is at the approximate midpoint of the workings, near the center of section 11. The location is accurate. The site corresponds to location 44 of Cobb (1972), and includes the location of Slate Creek, U.S. Bureau of Land Management MAS number 0020480035.

Geologic setting

Geologic description

Bedrock in the Slate Creek area consists chiefly of northeast-trending, lower Paleozoic or Proterozoic cherty argillite, calcareous siltstone and sandstone, chert, metavolcanic rocks, and limestone (Mertie, 1934; Chapman and others, 1982; Reifenstuhl and others, 1997 [RI 97-15a]). The rocks are cut and stacked by a series of thrust faults. The creek follows a fault for much of its length.
Slate Creek heads in lower Paleozoic chert, cherty argillite, and limestone. As the creek takes a northeasterly course and follows a fault, the north bank is calcareous siltstone and sandstone and the south bank is mainly chert. The placer deposit is centered at the approximate intersection of the northeasterly fault with a north-trending fault.
Slate Creek has a V-shaped valley near its mouth and an open valley farther upstream. According to Hess (1908), there are numerous quartz veins that he believed were the source of the gold. The gravels consist mainly of various sedimentary and metasedimentary rocks, along with some vein quartz and greenstone.
Mining began in 1902 (Collier, 1903) and was concentrated about 2 miles above the mouth of the creek. Drifting techniques were used initially (Hess, 1908). Prindle and Hess (1905) reported that the gravels were up to 26 feet thick with the gold concentrated in the bottom 3 feet of gravel and top 1.5 feet of bedrock. The gold-bearing gravels are both in bench and stream placers. The bench placers are only on the northwest side of the creek, 15 to 20 feet above the current channel, and consist of 5 feet of worn gravel overlain by 10-12 feet of muck. Mertie (1934) reported that the weathered bedrock contains clayey material that is yellowish brown and may contain gold. He hypothesized that much of the gold appears to have been derived from this bedrock.
The gold recovered from Slate Creek included nuggets that were several ounces in size (Mertie, 1934), and had a fineness of 915. Sluicing is aided by the usually good supply of water (one measurement equaled 560 miners inches) (Avnet, 1948). The placer also reportedly contains cobbles of barite, and nuggets of native silver and native copper (Prindle and Hess, 1905).
One property, mined on Slate Creek from 1912 continuously until 1941, consisted of 13 placer claims and stretched from the mouth of the creek upstream for 3.25 miles (Avnet, 1948). In the approximately 30 years that the property was mined, about 46,000 square feet of placer ground was mined by sluicing to wash away gravels to bedrock. Exposed nuggets were picked up by hand. This property subsequently was sold to Hilliard Avnet. By 1948, approximately 450,000 square feet of placer ground remained to be mined below the old workings. Two small deposits of gravel, one 205 square feet in surface area and the other a 17-cubic-yard body in a drift mine, respectively produced $141.69 and $121.00 in gold (gold at $35 per ounce) (Avnet, 1948). Assessment work by Hilliard Avnet was performed in 1957.
There were active mining claims on Slate Creek in 1967 (Heiner and others, 1968), and William Anderson ran a bulldozer on the creek in 1975 (Carnes, 1976). In 1984, Thanksgiving Mining Company used a backhoe to trench placer ground on Slate and Thanksgiving (TN118) creeks (Eakins and others, 1985). John Shilling sluiced on Slate Creek in 1990 (Swainbank and others, 1991). In 1997, Slate Creek Mining explored for placer gold and Don Harris mined (Swainbank and others, 1998). Don Harris stripped 5,000 cubic yards of overburden with bulldozers and a backhoe, and sluiced 6,500 cubic yards of gravel (Alaska Kardex files). Szumigala and Swainbank (1999) reported active mining on Slate Creek by Slate Creek Mining in 1998.
The only published estimate of production from Slate Creek was $15,000 worth of gold (about 725 ounces at $20.67 per ounce), mined through the fall of 1904 (Hess, 1908).
Newberry and Clautice (1997) analyzed four gold grains from Slate Creek by electron microprobe. Two of the grains are not zoned, contain bismuth-tellurium inclusions, and have respective silver and mercury compositions of 20 percent and 1 percent. They concluded that the grains were derived from a plutonic gold source like that at Elephant Mountain (TN067).
Geologic map unit (-150.170838022114, 65.3624064174039)
Mineral deposit model Placer Au (Cox and Singer, 1986; model 39a).
Mineral deposit model number 39a
Age of mineralization Quaternary.

Production and reserves

Workings or exploration
Both drift and surface workings occur on Slate Creek. Initial drift mining two miles from the mouth of Slate Creek was in gravels 26 feet thick (Prindle and Hess, 1905). Later reports (including Mertie, 1934) describe surface workings and ground sluicing operations. Mining on Slate Creek was reported from 1902-1916 and 1926-1941.
One property, mined on Slate Creek from 1912 continuously until 1941, consisted of 13 placer claims and stretched from the mouth of the creek upstream for 3.25 miles (Avnet, 1948). In the approximately 30 years that the property was mined, about 46,000 square feet of placer ground was mined by sluicing to wash away gravels to bedrock. Exposed nuggets were picked up by hand. This property subsequently was sold to Hilliard Avnet. By 1948, approximately 450,000 square feet of placer ground remained to be mined below the old workings. Two small deposits of gravel, one 205 square feet in surface area and the other a 17-cubic-yard body in a drift mine, respectively produced $141.69 and $121.00 in gold (gold at $35 per ounce) (Avnet, 1948).
There were active mining claims on Slate Creek in 1967 (Heiner and others, 1968), and William Anderson ran a bulldozer on Slate Creek in 1975 (Carnes, 1976). In 1984, Thanksgiving Mining Company used a backhoe to trench placer ground on Slate and Thanksgiving Creeks (Eakins and others, 1985). John Shilling sluiced on Slate Creek in 1990 (Swainbank and others, 1991). In 1997, Slate Creek Mining explored for placer gold and Don Harris mined (Swainbank and others, 1998). Don Harris stripped 5,000 cubic yards of overburden with bulldozers and a backhoe, and sluiced 6,500 cubic yards of gravel (Alaska Kardex files). Szumigala and Swainbank (1999) reported active mining on Slate Creek by Slate Creek Mining in 1998.
Indication of production Yes; small
Production notes Early records reported estimated recovery of $15,000 (or 725 ounces) worth of gold (at $20.67 per ounce) mined by the fall of 1904 (Hess, 1908).

References

MRDS Number A015223

References

Heiner, L.E., Wolff, E.N., and Lu, F.C.J., 1968, Mining regions and mineral commodities, in Heiner, L.E., and Wolff, E.N. eds., Final Report - Mineral Resources of Northern Alaska: Mineral Industry Research Laboratory, University of Alaska Report No. 16, p. 3-137.
Reporters G.E. Graham (ADGGS), D.J. Szumigala (ADGGS)
Last report date 2/10/2004