Point Astley

Prospect, Probably inactive

Commodities and mineralogy

Main commodities Ag; Cu; Pb; Zn
Ore minerals bornite; chalcocite; chalcopyrite; covellite; digenite; galena; pyrite; silver; sphalerite

Geographic location

Quadrangle map, 1:250,000-scale SD
Quadrangle map, 1:63,360-scale C-5
Latitude 57.70909
Longitude -133.63282
Nearby scientific data Find additional scientific data near this location
Location and accuracy The mineralization and workings of what is commonly called the Point Astley prospect occur discontinuously for about 1,500 feet near the shoreline southeast of Point Astley. The center of the workings is near the mine shown on the USGS 1:63,360 scale topographic map about a mile southeast of Point Astley. The location is accurate. The location of the workings and the mineral occurrences are shown on Figures 24 and 25 of Kimble and others (1984).

Geologic setting

Geologic description

The Point Astley prospect has been known since about 1900 (Spencer, 1906). It was intermittently explored by a succession of companies through 1984 (for details, see Spencer, 1906; Buddington, 1925; Herreid, 1962; Race, 1962; Kimble and others, 1984; Redman, 1988). There are two centers of mineralization separated by 700 feet, but much of the area is heavily vegetated and the continuity or extension of the known mineralization is uncertain. The prospect has been developed by 4, now-flooded shafts, one of which probably has a crosscut at depth, and 2 short adits. All of the workings date from before 1925. There has been no production but there was a test shipment to a smelter in about 1925.
The deposit consists of disseminated sulfides and small lenses of massive sulfides oriented along the foliation of the host rock. The massive sulfide lenses are no more than 3 feet long and 1 foot thick. The main sulfides are pyrite and sphalerite with minor galena and chalcopyrite. Locally in the richer portions of the deposit, bornite, chalcocite, covellite and digenite occur; native silver is reported. The host rock is green chloritic phyllite and black slaty phyllite, part of the Cretaceous greenschist unit of Brew and Grybeck (1984). Locally the sulfides have been remobilized and concentrated at the noses of small folds in the metamorphic rocks.
The northwest zone of mineralization has been explored by two shafts and a short the adit. Kimble and others (1984) sampled a 10-foot section of the mineralized rocks along the shoreline. A sample contained 0.48% copper, 0.11 percent lead, 1.65 percent zinc, and 0.2 ounces of silver per ton. A select sample from a lens of pyrite and sphalerite about 1.1 foot thick contained 0.44 per cent copper, 0.31 percent lead, 9.0 percent zinc, 0.17 ounce of gold per ton, and 1.45 ounces of silver per ton.
The other zone of mineralization is about 700 feet to the southeast near the shoreline. It has been explored by a shaft and two adits, only one of which was accessible to Kimble and others (1984). They collected a 30-foot sample that contained 0.07 percent copper, 1.72 percent zinc, and 0.18 percent silver. (The 1984 work by Kimble and others was restricted to the mineralization that could be seen then; few of the workings were accessible and they may have exposed higher grade mineralization.)
Geologic map unit (-133.634545382727, 57.7087529208685)
Mineral deposit model Metamorphosed, volcanogenic massive sulfide deposit?
Age of mineralization Unclear. The primary mineralization was remobilized during the Cretaceous event that formed the metamorphic host rocks. The age of the protolith is uncertain, as is whether the primary mineralization was syngenetic or epigenetic.

Production and reserves

Workings or exploration The prospect has been developed by 4, now-flooded shafts, one of which probably has a crosscut at depth, and 2 short adits. All of the workings date from before 1925. A succession of companies have looked at or owned the property into the 1980s but there probably has been no substantial exploration since the 1920s.
Indication of production None
Production notes No recorded production; there was a test shipment to a smelter in 1925.

Additional comments

The prospect is in the Tracy Arm-Fords Terror Wilderness Area which is closed to mineral exploration and mining.


MRDS Number A013333


Redman, Earl, 1988, History of the mines and miners in the Juneau gold belt: Juneau, Alaska, privately printed, 294 p.
Reporters Donald Grybeck (U.S. Geological Survey)
Last report date 10/8/2004