Ironside Bench; Ironside Bar Mine, Koyukuk Mining District, Yukon-Koyukuk Census Area, Alaska, USAi

Regional Level Types
Ironside Bench; Ironside Bar Mine	Mine
Koyukuk Mining District	Mining District
Yukon-Koyukuk Census Area	Census Area
Alaska	State
USA	Country

See also: Gold Bench (BT003).
Location: The Ironside Bench located along the south side of the South Fork Koyukuk River about a mile upstream from Gold Bench. Both Ironside Bench and Gold Bench are marked on the current (1970, photorevised 1975) Bettles D-2 topographic map. The location is accurate.
Geology: The high channel which constitutes the Ironside Bench placer is about 30 feet higher than the current level of the South Fork Koyukuk River. It is about at the same level as the nearby Gold Bench channel (BT003). Reed (1938) suggests that the channels at both locations are the same. River-washed gravel at Ironside Bench is heavy, coarse and waterworn, with few large boulders. The gravel lies on a layer of blue clay, which Reed (1938) suspected is decomposed shale. The depth to bedrock varies from 6 to 30 feet ; the upper 5 to 6 feet is muck and ice. The gold is waterworn, fine and flaky; it occurs throughout the gravel but is found mostly at the top of the clay. Mining was generally by hand methods. Mining by ground sluicing and shoveling into sluice boxes was being done in 1937 ; about 40 acres were said to have been mined by that time (Reed, 1938). Grybeck (1977) indicated mining activity through 1975. The only production figures available are Maddren's (1913), who indicates that a total of $2,000 (about 100 oz.) in gold had been recovered by 1909. No figures are available for later production. Reed (1938) reported that the value of the ground ranged from 25 to 50 cents per square foot of bedrock and that the average fineness of the gold is 907.5.
Workings: Mining was generally by hand methods. Mining by ground sluicing and shoveling in was being done in 1937 and about 40 acres were said to have been mined by that time (Reed, 1938). Grybeck (1977) indicated mining activity through 1975.
Age: Quaternary.
Production: The only production figures available are Maddren's (1913), who indicated that a total of $2,000 (about 100 oz.) in gold had been recovered by 1909. No figures are available for later production. Reed (1938) reported that the value of the ground ranged from 25 to 50 cents per square foot of bedrock foot and that the average fineness of the gold is 907.5.

Commodities (Major) - Au
Development Status: Yes; small
Deposit Model: Placer Au (Cox and Singer, 1986; model 39a)

Other Databases

Link to USGS - Alaska:	BT004

Other Regions, Features and Areas containing this locality

References