|Quadrangle map, 1:250,000-scale||MZ|
|Quadrangle map, 1:63,360-scale||D-3|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||Gold was placer mined in the late 19th and early 20th centuries on what was then called Florence Bar, a prominent bar of sand on the west side of the Koyukuk River across from Rock Island Point. There apparently were several mines on the bar. The mines are in the SE1/4 of section 1, T. 6 N., R. 21 E., Kateel River Meridian. The location is accurate within 2,000 feet. It corresponds to location 2 of Cobb (1972).|
The Florence Bar placer mines were on a gravel bar in the Koyukuk River across the river from Rock Island Point. Most of the immediate area is covered by Quaternary flood plain, colluvium, alluvium, and terrace deposits (Patton and others, 1977). Bedrock at Rock Island Point includes Cretaceous pillow basalt and andesite flows; andesitic tuff, volcanic conglomerate and breccia; chert and fine-grained cherty tuff; and coquinoidal limestone. The rocks are widely altered to dark green hornfels. To the northeast, the andesitic volcanic rocks are in contact with Cretaceous quartz-pebble conglomerate, quartzose sandstone, andesitic and dacitic volcanic rocks, volcanic graywacke, and mudstone (Patton and Miller, 1966; Patton and others, 1977). The Indian Mountain granitic pluton, and associated latite dikes up to several hundred feet thick, intrude the Cretaceous stratified rocks about 8 miles northeast of Rock Island Point. The pluton is exposed no closer than five miles from the Koyukuk River, although several small dikes crop out on or near the river's edge (Patton and Miller, 1966).Placer gold was known in the Koyukuk Basin in the 1890s or earlier (Schrader, 1904). It was first discovered in the sand bars of the Koyukuk River, where the river gradient is low, perhaps 5 feet per mile. The Florence Bar placer area was one of three bars (Florence, Hughes, and Tramway) mined before 1898, the Florence Bar mines produced a total of about $4,000 in gold (approximately 200 ounces of gold at $20.67 per ounce) (Maddren, 1910 [B 442]; Cobb, 1975). Early miners described the gold from Florence Bar as very fine, suggesting that it traveled a substantial distance (Smith, 1913). The source of the gold is unknown.
|Geologic map unit||(-154.344326500947, 65.945051848004)|
|Mineral deposit model||Placer Au (Cox and Singer, 1986; model 39a)|
|Mineral deposit model number||39a|
|Age of mineralization||Quaternary.|
|Workings or exploration||Placer gold was known in the Koyukuk Basin in the 1890s or earlier (Schrader, 1904). It was first discovered in the sand bars of the Koyukuk River. There is no record of the type of workings or their extent.|
|Indication of production||Yes; small|
|Production notes||About $4,000 in gold (approximately 200 ounces of gold at $20.67 per ounce) was recovered from Florence Bar before 1898 (Maddren, 1910 [B 442]; Cobb, 1975). The total gold production from the placer mines on Florence Bar is unknown.|
Additional commentsThis site is the Florence Bar, U.S. BLM MILS location 0020470014 (Oddenino and others, 1995; Interagency Minerals Coordinating Group, 2004).
Cobb, E.H., 1972, Metallic mineral resources map of the Melozitna quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-396, 1 sheet, scale 1:250,000.
Cobb, E.H., 1975, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in five quadrangles in west central Alaska (Hughes, Kotzebue, Melozitna, Selawik, Shungnak): U.S. Geological Survey Open-File Report 75-627, 58 p.
Interagency Minerals Coordinating Group, 2004, Alaska Mineral Locations Database [MAS (Minerals Availability System) and MILS (Mineral Industry Location System)], http://imcg.wr.usgs.gov/dem.html (select Melozitna quadrangle).
Maddren, A.G., 1910, The Koyukuk-Chandalar gold region: U.S. Geological Survey Bulletin 442-G, p. 284-315.
U.S. Bureau of Mines, 1995, Minerals Availability System / Minerals Industry Location System CD-ROM MAS/MILS CD-ROM: U.S. Bureau of Mines Special Publication 95-12.
Patton, W.W., Jr., and Miller, T.P., 1966, Regional geologic map of the Hughes quadrangle, Alaska: U.S. Geological Survey Miscellaneous Investigations Series Map I-459, 1 sheet, scale 1:250,000.
Patton, W.W., Jr., Miller, T.P., Chapman, R.M., and Yeend, W., 1977, Geologic map of the Melozitna quadrangle, Alaska: U.S. Geological Survey Open-File Report 77-147, 1 sheet, scale 1:250,000.
Schrader, F.C., 1904, A reconnaissance in northern Alaska across the Rocky Mountains, along Koyukuk, John, Anaktuvuk, and Colville rivers and the Arctic coast to Cape Lisburne, in 1901, with notes by W.J. Peters: U.S. Geological Survey Professional Paper 20, 139 p.
|Reporters||G.E. Graham, D.J. Szumigala (Alaska Division of Geological and Geophysical Surveys)|
|Last report date||6/4/2004|