Pringle Bench

Mine, Active

Alternative names

Jones & Boyle

Commodities and mineralogy

Main commodities Ag; Au; Sb
Ore minerals gold; stibnite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale WI
Quadrangle map, 1:63,360-scale B-1
Latitude 67.4746
Longitude -150.2204
Nearby scientific data Find additional scientific data near this location
Location and accuracy This mine is on the north side of lower Smith Creek, about 0.5 mile east of Nolan; it is near the northeast corner of section 33, T. 31 N., R. 12 W. The location is accurate. Kurtak and others (2002) include a detailed map of the mine as their figure I-10.

Geologic setting

Geologic description

As the Jones and Boyle, this mine was described prior to 1988 as a series of quartz-stibnite veins that were exposed during placer mining sometime prior to 1943 (Ebbley and Wright, 1948). The veins apparently were still exposed in the old placer cuts as late as 1974. Ebbley and Wright describe six, parallel quartz-stibnite veins, 3-4 inches wide; the stibnite is concentrated in the central 1.5 to 2 inches of the veins. W. W. Patton Jr.'s, U. S. Geological Survey field notes in 1953 indicate that the veins are as wide as 1 foot and that their stibnite core is as wide as 4 inches (Bliss and others, 1988). The veins are in joints and locally are offset by cross faults (Bliss and others, 1988). Six samples of vein material contained 0.02 to 0.06 part per million (ppm) gold and from less than 0.1 ppm to 0.2 ppm silver (Bliss and others, 1988). Two samples of bedrock near the veins contained 0.03 ppm gold. Samples across the veins contained 33.8 to 44.5 percent antimony (Mulligan, 1974).
The host rocks at the Pringle Bench (Jones & Boyle) Mine are Devonian phyllite, schist, and metasiltstone (Dillon and Reifenstuhl, 1990). The gold-stibnite mineralization occurs as distinct veins parallel to and along a structural zone 120 to 350 feet wide that strikes northeast and dips 50 to 85 degrees southeast (Bundtzen, 2008, 2009). Both stibnite (only) and quartz-stibnite veins are present; minor arsenopyrite occurs in them. On the nearby Workman's Bench prospect, there are veins of massive stibnite up 15 inches thick that assayed up to 2.86 ounces of gold per ton. Four major, parallel veins across a width of about 100 feet and a strike length of about 1,100 feet were cut in the 41 drill holes and the underground workings of Workman's Bench (WI115); there were numerous gold-stibnite(-quartz) veinlets between the major veins. When Silverado was working on the Workman's Bench prospects, they drilled 8 holes on Pringle Bench. At the Pringle Bench Mine, two major stibnite-gold(-quartz) veins were intersected that extended for about 600 feet along strike. The mineralization at the Workman's Bench and Pringle Bench only could be followed in the drill holes but the orientation and characteristics of the mineralization at the two sites demonstrate that it is probably continuous over a distance of at least 1,600 feet through the two sites. Soil geochemistry and geophysical data suggest that the mineralization continue further northeast.
Bundtzen (2009) estimated that Pringle Bench has an 'inferred resource' of 6,308 tons with an average grade of 12.78 percent antimony and 0.088 ounce of gold per ton.
Five tons of stibnite ore were recovered from sluice operations somewhere on upper Smith Creek and shipped during World War II (Joesting, 1943). Joesting attributed at least some of this production to this property, then known as the Jones & Boyle prospect. However, his description of its source on upper Smith Creek contradicts the location of the Jones & Boyle prospect described by Ebbley & Wright (1948). More likely, the source of the stibnite was the unnamed prospect at the head of Smith Creek on Midnight Dome (WI130). The information is so vague however, that the ore may have come ore or more of the stibnite prospects near Smith Creek (WI114, WI115, or WI130). Based on a personal communication from E. Armstrong, about 35 drums of stibnite ore was hand-cobbed from the Pringle Bench Mine in the 1980s and possibly shipped to Texas (Kurtak and others, 2002).
Geologic map unit (-150.223149431871, 67.4741737215151)
Mineral deposit model Sb-Au vein (Nokleberg and others, 1987).
Age of mineralization Devonian or younger based on the age of the host rocks.
Alteration of deposit No alteration is mentioned.

Production and reserves

Workings or exploration Before 1999, the Pringle Bench Mine apparently was only sampled by government and industry. In 1999, the U.S. Bureau of Land Management began work in the area that included soil sampling and an airborne geophysical survey (Kurtak and others, 2002). Their data encouraged Silverado Gold Mines, Ltd., who was placer mining along Nolan Creek, to more aggressively search for the lode source of the placer gold. They concentrated their work on Pringle Bench and Workman's Bench (WI115), about 1,500 feet to the southwest where auriferous stibnite was also known to occur. Silverado drilled 8 core holes on the Pringle Bench Mine that intersected several auriferous stibnite veins.
Indication of production Yes
Reserve estimates Bundtzen (2009) estimated that Pringle Bench Mine has an 'inferred resource' of 6,308 tons with an average grade of 12.78 percent antimony and 0.088 ounce of gold per ton.
Production notes Five tons of stibnite ore were recovered from sluice operations somewhere on upper Smith Creek and shipped during World War II (Joesting, 1943). Joesting attributed at least some of this production to this property, then known as the Jones & Boyle prospect. However, his description of its source on upper Smith Creek contradicts the location of the Jones & Boyle prospect described by Ebbley & Wright (1948). More likely, the source of the stibnite was the unnamed prospect at the head of Smith Creek on Midnight Dome (WI130). The information is so vague however, that the ore may have come ore or more of the stibnite prospects near Smith Creek (WI114, WI115, or WI130). Based on a personal communication from E. Armstrong, about 35 drums of stibnite ore was hand-cobbed from the Pringle Bench Mine in the 1980s and possibly shipped to Texas (Kurtak and others, 2002).

References

MRDS Number A011940

References

Kurtak, J.M., Klieforth, R.F., Clark, J.M., and Maclean, E.A., 2002, Mineral investigations in the Koyukuk mining district, northern Alaska: Final Report: U.S. Bureau of Land Management Technical Report 50, v. 1 and 2, 845 p.
Reporters J.M. Britton (Anchorage); D.J. Grybeck (Contractor, USGS)
Last report date 2/1/2011