Rossness & Larson

Mine, Inactive

Commodities and mineralogy

Main commodities Au
Other commodities Ag
Ore minerals arsenopyrite; gold; pyrite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale SV
Quadrangle map, 1:63,360-scale C-2
Latitude 59.56
Longitude -150.59
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Rossness and Larson mine is about 0.2 miles north of VAMB Mid on the north shore of the North Arm of Nuka Bay. The property consists of three short adits, numerous open cuts, and the ruins of the mill and camp. Two of the adits are near the beach at 30 and 50 feet above sea level; they are on each side of a small stream which drains into the cove. The third adit is at an elevation of 107 feet and about 250 feet northwest of the lower tunnels.

Geologic setting

Geologic description

The host rock of the prospect is graywacke and thin slate interbeds of the Cretaceous Valdez Group (Richter, 1970). The quartz veins of this prospect consist of white crystalline quartz with various amounts of sulfides. Arsenopyrite is the dominate sulfide with minor amounts of pyrite. Gold occurs as free gold and associated with arsenopyrite. The veins at this prospect are lens shaped and generally follow the bedding which strikes N30W and dips 67S (Pilgrim, 1933). They range from less than one inch to over four feet in width.
The southwest adit is 30 feet in length and follows a stockwork of parallel quartz veins. The veins range in width from 0.1 to 0.5 foot and strike N30W and dip 67S. A composite sample across four of these veins assayed 26 ppm gold (Richter, 1970). The northwest adit is caved and appears to have followed a single quartz-arsenopyrite vein that trends east-west and dips 80S. Richter (1970) sampled this vein and it contained 0.05 ppm gold.
The upper adit at 110 foot elevation trends east-west and dips 80S. There are no assay results from this adit.
North of the two adits near the beach, there is a pyritized, light colored dike swarm which trends N20W. A sample of this dike swarm contained 0.028 ounces of gold per ton (Pilgrim,1933).
Geologic map unit (-150.59210020582, 59.5594164949227)
Mineral deposit model Low-sulfide, Au-quartz vein (Cox and Singer, 1986; model 36a)
Mineral deposit model number 36a
Age of mineralization Tertiary; Boden and others (1991) report other veins in the district are about 55 m.y. old.
Alteration of deposit Borden and others (1991) report carbonization, sulfidization, sericitization, and silicification of the wall rock adjacent to the veins.

Production and reserves

Workings or exploration According to Pilgrim, (1933) the mine produced some gold during the 1931-33 period but it was inactive during Capps' 1936 visit (Capps, 1938, p. 32). Three adits totaling 170 feet in length and numerous surface cuts occur on the property. Composite samples by Richter (1970) of the southwest veins assayed 26 ppm gold. Samples by Pilgrim (1933) assayed between 0.08 and 0.064 ounces of gold and 0.40 ounces of silver per ton. A sample of the pyritic dike assayed 0.028 ounces of gold per ton (Pilgrim,1933).
Indication of production Undetermined
Reserve estimates None.

Additional comments

This prospect is within the Kenai Fjords National Park; the park is closed to mineral entry.

References

MRDS Number A010573

References

Pilgrim, E.R., 1933, Nuka Bay district, in Stewart, B. D., Making mining investigations and mine inspection in Alaska, biennium ending March 31, 1933: Alaska Territorial Department of Mines Annual Report 1933B, p. 26-51.
Reporters Jeff A. Huber (Anchorage)
Last report date 2/17/1999