Gold Nugget

Prospect, Undetermined

Alternative names

South quarry

Commodities and mineralogy

Main commodities Ag; Au
Other commodities Pb; Zn
Ore minerals galena; pyrite; sphalerite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale KC
Quadrangle map, 1:63,360-scale B-5
Latitude 55.309
Longitude -131.575
Nearby scientific data Find additional scientific data near this location
Location and accuracy This site is in section 3, T. 76 S., R. 91 E., of the Copper River Meridian. It includes the Gold Nugget prospect and the South quarry occurrence. The Gold Nugget prospect is on the Tongass Narrows shoreline of Revillagigedo Island, about 1.8 miles northwest of Mountain Point. The South quarry occurrence is at an elevation of about 100 feet, 0.25 mile southeast of the Gold Nugget prospect. The coordinates are for the Gold Nugget prospect. The Gold Nugget prospect corresponds to loc. 74 in Elliott and others (1978), and to loc. 284 in Maas and others (1995). The South quarry occurrence is loc. 285 in Maas and others (1995). The location of the Gold Nugget prospect is accurate within 0.1 mile.

Geologic setting

Geologic description

The country rocks in this part of Revillagigedo Island are mainly marine, andesitic or basaltic metavolcanic rocks and interbedded pelitic sedimentary rocks that are intruded by Cretaceous stocks, sills, and dikes of feldspar-porphyritic granodiorite, and by a stock and probably related plugs of Tertiary gabbro (Berg and others, 1988). The strata and some of the granodiorite were regionally metamorphosed to greenschist grade in Late Cretaceous time. These rocks subsequently were contact metamorphosed to hornblende hornfels: locally, near some of the Cretaceous granodiorite contacts, and, more widely, peripheral to the Tertiary gabbro. The premetamorphic age of the strata is uncertain. Berg and others (1988) note that they closely resemble Upper Jurassic to mid-Cretaceous flysch and volcanic rocks nearby on Gravina Island. The country rocks are cut by a high-angle fault along Tongass Narrows that displays about 4 miles of right-lateral offset.
Maas and others (1995, p. 194, 197) describe the Gold Nugget deposit as irregular quartz ladder veins hosted in a 30-foot-thick porphyritic dike that cuts the foliation of slate country rock. The veins carry lenses and disseminations of pyrite, sphalerite, and galena. The dike is exposed for a length of 150 feet. Samples of the deposit assayed as high as 14.05 ppm Au, 7.9 ppm Ag, 829 ppm Pb, and 1585 ppm Zn, but most samples were much lower in grade. The Gold Nugget prospect was developed in the early 1900s by opencuts and two shafts that subsequently were covered or plugged during housing development. Small amounts of gold probably were recovered early in the century, but there is no public record of any production.
At the South quarry occurrence, a small rock sample of unspecified type contained 8.1 ppm Au, 31.5 ppm Ag, 1.04% Pb, and 2.08% Zn (Maas and others, 1995, p. 201).
Geologic map unit (-131.576684885803, 55.3086538963261)
Mineral deposit model Polymetallic veins (Cox and Singer, 1986; model 22c)
Mineral deposit model number 22c
Age of mineralization Cretaceous or younger.

Production and reserves

Workings or exploration
The Gold Nugget prospect was developed in the early 1900s by opencuts and two shafts that subsequently were covered or plugged during housing development. Samples of the deposit assayed as high as 14.05 ppm Au, 7.9 ppm Ag, 829 ppm Pb, and 1585 ppm Zn, but most samples were much lower in grade (Maas and others, 1995, p. 197, 201).
At the South quarry occurrence, a small rock sample of unspecified type contained 8.1 ppm Au, 31.5 ppm Ag, 1.04% Pb, and 2.08% Zn (Maas and others, 1995, p. 201).
Indication of production Undetermined
Production notes Small amounts of gold probably were recovered in the early 1900s, but there is no public record of any production.

References