Claim Point

Mine, Inactive

Alternative names

Reef

Commodities and mineralogy

Main commodities Cr
Other commodities Fe
Ore minerals chromite; magnetite
Gangue minerals olivine; pyroxene

Geographic location

Quadrangle map, 1:250,000-scale SV
Quadrangle map, 1:63,360-scale A-5
Latitude 59.21
Longitude -151.82
Nearby scientific data Find additional scientific data near this location
Location and accuracy These chromite deposits occur on a small peninsula on the northern shore of Port Chatham in the SW1/4 of section 21, T. 11 S., R. 15 W., of the Seward Meridian. Most of the chromite lens and layers are found on the northeast side of the peninsula near the old mill and wharf. This is location 1 of Cobb (1972, MF-397) and is accurate to within half a mile.

Geologic setting

Geologic description

The chromite at Claim Point occurs in dunite that is part of the informally named Border Ranges ultramafic and mafic complex of Burns (1985). The Border Ranges complex is at least Jurassic in age. The complex is faulted at the base and there are many small northeast-trending, high-angle faults which offset the chromite layers. In general, the chromite layers strike northeast and dip nearly vertical.
Most of the production in the area has occurred from the Reef mine where the ore body strikes N76E with a near vertical dip. Its length is about 135 feet and the width ranges from three to 35 feet. The chromic oxide content of the ore as shipped, ranged from 42 to 49 percent (Guild, 1942).
Foley and Barker (1985) estimates there is 82,000 metric tons of ore that grades from 5 to 30% chromic oxide.
Geologic map unit (-151.822115387555, 59.2093292959436)
Mineral deposit model Podiform chromite (Cox and Singer, 1986; model 8a)
Mineral deposit model number 8a
Age of mineralization Early Jurassic.
Alteration of deposit Serpentinization and spillitic alteration is common.

Production and reserves

Workings or exploration Production totaled 2,000 metric tons from the Reef and Bluff mines from 1916 to 1918; development included a wharf and camp. Some drilling was done during WW II by the U.S. Bureau of Mines. Anaconda Minerals flew regional airborne geophysics in the early 1980s which showed a major magnetic high underlying the outer part of Port Chatham bay (Foley, 1992).
Indication of production Yes; small
Reserve estimates There are conflicting estimates of the remaining reserves for this property. Foley (1992, p. 38) estimates a total resource of 82,000 metric tons of ore that grades 17.8% chromic oxide, while MacKevett and others (1978, p. 17) estimate a resource of 260,000 tons at 17.8% chromic oxide.
Production notes Two thousand metric tons of chromite ore was produced in 1917 and 1918 (Foley, 1992, p. 38).

References

MRDS Number A010671

References

Burns, L.E., 1985, The Border Ranges ultramafic and mafic complex, south-central Alaska; Cumlative fractionates of island-arc volcanics: Canadian Journal of Earth Science, v. 22, p.1020-1038.
Reporters Jeff A. Huber (Anchorage)
Last report date 2/25/1999