Location: The Hill Top occurrence is located on the southwest flank of a prominent, unnamed hill east of the upper reaches of the south fork of the Oskawalik River. It is about 3.6 miles north of the Mountain Top Mine (SM058), at an elevation of about 2,200 feet, about 0.3 mile west of the center of section 30, T. 16 N., R. 48 W., of the Seward Meridian. The location is accurate.
Geology: The Hill Top occurrence consists of a rhyolite breccia zone in a felsic sill complex that intrudes sandstone and shale of the Upper Cretaceous, Kuskokwim Group (Cady and others, 1955; Decker and others, 1995). The sills are part of a large, prominent northeast-trending sill complex in the central Sleetmute quadrangle (Cady and others, 1955). One grab sample of rhyolite breccia collected by the Alaska Division of Geological and Geophysical Surveys contained 927 parts per million (ppm) arsenic, 300 parts per billion (ppb) gold, 600 ppb silver, and 2.9 ppm mercury (Robinson, 1984 [RI 84-11]; Miller and others, 1989).
Workings: The Alaska Division of Geological and Geophysical Surveys investigated the Hill Top occurrence in the 1980s (Robinson, 1984 [RI 84-11]; Decker and others, 1995).
Age: Unknown. Decker and others (1995) report 40K/40Ar ages of from 67 to 70 Ma for a nearby sill swarm that is probably similar to the sills at this occurrence.

Commodities (Major) - As, Au; (Minor) - Ag, Hg
Development Status: None

Select Mineral List Type

Standard Detailed Gallery Strunz Chemical Elements

Commodity List

This is a list of exploitable or exploited mineral commodities recorded at this locality.

ⓘ Arsenic

ⓘ Mercury

ⓘ Silver

Mineral List

ⓘ Arsenopyrite

1 valid mineral.

Detailed Mineral List:

ⓘ Arsenopyrite

Formula: FeAsS

References:

(2008) Alaska Resource Data File (ARDF) Open-File Report 2008-1225. US Geological Survey

Gallery:

List of minerals arranged by Strunz 10th Edition classification

Group 2 - Sulphides and Sulfosalts
ⓘ	Arsenopyrite	2.EB.20	FeAsS

List of minerals for each chemical element

S	Sulfur
S	ⓘ Arsenopyrite	FeAsS
Fe	Iron
Fe	ⓘ Arsenopyrite	FeAsS
As	Arsenic
As	ⓘ Arsenopyrite	FeAsS

Other Databases

Link to USGS - Alaska:	SM059

Other Regions, Features and Areas containing this locality

North AmericaContinent

North America PlateTectonic Plate

Farewell buried DomainDomain
Koyukuk ArcsVolcanic Arc

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References

Cady, W.M., Wallace, R.E., Hoare, J.M., and Webber, E.J., 1955, The central Kuskokwim region, Alaska: U.S. Geological Survey Professional Paper 268, 132 p. Decker, J.E., Reifenstuhl, R.R., Robinson, M.S., Waythomas, C.F., and Clough, J.G., 1995, Geology of the Sleetmute A-5, A-6, B-5, and B-6 quadrangles southwestern Alaska: Alaska Division of Geological and Geophysical Surveys Professional Report 99, 16 pages, one sheet, scale 1:63,360. Miller, M.L., Belkin, H.E., Blodgett, R.B., Bundtzen, T.K., Cady, J.W., Goldfarb, R.J., Gray, J.E., McGimsey, R.G., and Simpson, S.L., 1989, Pre-field study and mineral resource assessment of the Sleetmute quadrangle, southwestern Alaska: U.S. Geological Survey Open-File Report 89-363, 115 p., 3 plates, scale 1:250,000. Robinson, M.S., 1984, Rock, pan-concentrate, and stream-sediment geochemistry, Sleetmute B-6 quadrangle, Alaska: Alaska Division of Geological and Geophysical Surveys Report of Investigations 84-11, 1 sheet, scale 1:40,000.

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