Wackwitz; Silver King; Little Jim Prospect, Fairbanks Mining District, Fairbanks North Star Borough, Alaska, USAi

Regional Level Types
Wackwitz; Silver King; Little Jim Prospect	Prospect
Fairbanks Mining District	Mining District
Fairbanks North Star Borough	Borough
Alaska	State
USA	Country

Location: The Wackwitz prospect is located on the divide between Twin Creek and Bedrock Creek, approximately one-quarter mile east of Cleary Summit.
Geology: By 1912, William Jackson had staked the Silver King claim and exposed a flat-lying bed of massive sulfides (Times Publishing Company, 1912). This occurrence contained arsenopyrite, stibnite, galena, pyrite and at least one lead sulfosalt; it was conformable to the surrounding schists (Smith, 1913; B 525). The sulfide bed was one foot thick and was largely oxidized to scorodite and antimony oxides with borders of quartz and sulfide stringers in the surrounding schist (Chapin, 1914). By 1916, the prospect was known as the Silver King or Little Jim prospect and consisted of two open cuts approximately 250 feet apart, both of which hosted a flat-lying sulfide horizon in the metamorphic country rocks (Mertie, 1918). The southeastern open cut exposed 12 inches of massive sulfides, trending east-west and dipping 25 S. A shaft was sunk about 25 feet south of the open cut to intersect the horizon. The other open cut, 250 feet to the northeast exposed a 4-inch-thick sulfide-bearing seam with euhedral quartz crystals in its matrix. This occurrence strikes N 45 E and dips at a low angle to the southeast. The mica schist country rock is heavily stained with iron-oxides for 6 to 7 inches on either side of the sulfide horizon and assays $6 to $7 per ton in gold (0.29 to 0.33 ounces of gold per ton). The sulfide horizons on the Wackwitz prospect contained extremely high silver contents relative to gold (Mertie, 1918). In the early 1950's, the prospect was known as the 'Polaris' lead-silver prospect when 34 tons of hand-picked lead-silver ore was produced from two open cuts, approximately 1300 feet apart (Saunders, 1954). The mineral deposit was said to strike about N 80 W and dip 20 S. The vein-filling was mostly sulfides, mainly galena and stibnite. The vein had an average thickness of about 8 inches. Smelter returns of sorted ore contained 0.10 to 0.20 ounces of gold per ton, 16.97 to 98.95 ounces of silver per ton and 23.35% to 47.7% lead (Saunders, 1954, p. 5). Metz and Robinson (1980) examined the Wackwitz prospect and noted the mineralization consisted of a one-meter-thick massive sulfide horizon in quartz muscovite schist striking N 60 E and dipping flatly to the southeast. Polished sections of the mineralization contained stibnite, jamesonite, galena, sphalerite, arsenopyrite and pyrite which occur in discrete bands. By volume stibnite constitutes 90% of the lens, sphalerite 5%, galena 2% and jamesonite, arsenopyrite and pyrite 1% each. In 1983, a 100-pound metallurgical sample was collected from a 12-inch thick horizon of massive sulfide on the Wackwitz prospect. This sample assayed 3 to 5 ounces of silver per ton, 0.08 ounces of gold per ton, 5 to 10% arsenic, 1 to 10% antimony and greater than 10% lead (Wu-Ming, 1983). Oxide phases present included senarmontite, scorodite, cervantite and bindhemite, while metallic phase minerals included arsenopyrite, pyrite, jamesonite, boulangerite, tetrahedrite, galena, stibnite and sphalerite. Gold was associated as free inclusions in arsenopyrite; silver was present in tetrahedrite. Crushing and grinding tests indicated precious metals were most abundant in the minus-265-mesh fraction. Thiourea leaching of the Wackwitz ores indicated optimum silver recovery of only 40% on a 24 hour leach. Gold recovery by thiourea leaching was not investigated (Wu-Ming, 1983).
Workings: By 1916, the prospect was known as the Silver King or Little Jim prospect and consisted of two open cuts approximately 250 feet apart (Mertie, 1918). The prospect was known as the 'Polaris' lead-silver prospect in the early 1950's when 34 tons of hand-picked lead-silver ore was produced from two open cuts, approximately 1300 feet apart (Saunders, 1954).
Alteration: The mica schist country rock is heavily iron oxide stained for 6 to 7 inches on either side of the sulfide horizon.
Production: About 34 tons of hand-picked lead-silver ore was produced in 1951 and 1952 (Saunders, 1954, p. 3). Smelter returns indicated gold values from 0.10 to 0.20 ounces of gold per ton, silver from 16.97 to 98.95 ounces of silver per ton and lead from 45.89 to 143.45 ounces of lead per ton (Saunders, 1954, p. 5).

Commodities (Major) - Ag, Pb, Sb; (Minor) - Au, Zn
Development Status: Yes; small
Deposit Model: Massive sulfide horizon hosted by quartz muscovite schist.

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Link to USGS - Alaska:	LG090

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References