Lucky Chance

Mine, Undetermined

Commodities and mineralogy

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

Geographic location

Quadrangle map, 1:250,000-scale PA
Quadrangle map, 1:63,360-scale D-4
Latitude 56.94969
Longitude -135.05146
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Lucky Chance Mine is shown by symbol on the 1:63,360-scale topographic map. It is near the south end of the southern of the Last Chance Lakes and about 0.5 mile south of the center of section 5, T. 57 S., R. 66 E.

Geologic setting

Geologic description

This deposit is one of many of similar deposits (PA002 to PA018) scattered over an area of about 6 square miles at the head of Silver Bay (Bittenbender and others, 1999). The deposits are gold-quartz veins with sparse sulfides, usually only pyrite and arsenopyrite. Samples that have been analyzed with modern methods usually show anomalous arsenic even if arsenopyrite is not identified in the rocks, and several parts per million mercury. The veins are often parallel to the bedding of the host rock which is graywacke and argillite of the Sitka Graywacke of Cretaceous age (Loney and others, 1975). Many of the so-called veins in the early literature are actually fault zones with lenses of quartz or concentrations of quartz stringers along the fault zone. Prospecting began in the area in 1871. The Stewart Mine (PA012) was located in 1872 and it was the first lode-gold mine in Alaska. The Silver Bay area has been prospected intermittently to the present but the veins are relatively small and most are low grade. The area has produced relatively little gold, many of the properties have not been active since before 1900, and there has been no production since the early 1940s.
The Last Chance Mine was first staked in 1874 and went through a succession of owners to 1904. By 1885, it was developed by a 25-foot shaft and a 30-foot drift (DeArmond, 1997). By 1887, the property had a 5-stamp mill and 60 tons of ore was produced from two adits. By 1904, there was a 10-stamp mill, a sawmill, and a waterpower generator, and about 1,200 tons of ore had been produced above the main adit which was called the No. 2 tunnel (Becker, 1897; Wright and Wright, 1905; Roehm, 1940). A 3,000- to 4,000-foot tram was built from the mouth of this adit to the mill below and a corduroy road was built to the mine from the head of Silver Bay. The workings include: a 468-foot adit, the No. 2 Tunnel; a 45-foot adit higher on the hillside; a shaft; a glory hole at the top of a stope about 50 feet wide that extends vertically for about 80 feet; and numerous surface trenches. The property was under new ownership in 1940 (Roehm, 1940) but most of the development and production probably took place before the early 1900s. There are no records but there certainly was some production.
The deposit at the Last Chance Mine is along a prominent fault zone that strikes about N45W, dips 80-85NE, and cuts graywacke and phyllite (Roehm, 1940). Numerous quartz stringers occur in the fault zone, many at nearly right angles to it, and the stope that was mined coincides with the greatest concentration of these stringers. Many of the quartz stringers persist into phyllite in the hanging wall of the fault. The quartz is generally milky white and often includes partings of the graywacke and phyllite country rock. Minor pyrite and arsenopyrite occur as thin seams and irregular masses up to 0.5 inch thick in the quartz which also carries visible gold. Several samples taken by Roehm (1940) along the hanging wall of the fault/vein contained 0.17 to 1.72 ounces of gold per ton.
In the late 1990s, the underground workings were caved but Bittenbender and others (1999) collected several surface samples. Two hand-selected samples from the dump contained 19.3 and 16.9 parts per million (ppm) gold. A sample of concentrates from the mill site contained 26.5 ppm gold, 13 ppm silver, 1,250 ppm lead, and more than 1 percent arsenic.
Geologic map unit (-135.053222392311, 56.9493215489465)
Mineral deposit model Low-sulfide, gold-quartz vein (Cox and Singer, 1986; model 36a).
Mineral deposit model number 36a
Age of mineralization Cretaceous or younger based on the age of the host rocks.

Production and reserves

Workings or exploration The Last Chance Mine was first staked in 1874 and went through a succession of owners to 1904. By 1885, it was developed by a 25-foot shaft and a 30-foot drift (DeArmond, 1997). By 1887, the property had a 5-stamp mill and 60 tons of ore was produced from two adits. By 1904, there was a 10-stamp mill, a sawmill, and a waterpower generator, and about 1,200 tons of ore had been produced above the main adit which was called the No. 2 Tunnel (Becker, 1897; Wright and Wright, 1905; Roehm, 1940). A 3,000- to 4,000-foot tram was built from the mouth of this adit to the mill below and a corduroy road was built to the mine from the head of Silver Bay. The workings include: a 468-foot adit, the No. 2 tunnel; a 45-foot adit higher on the hillside; a shaft; a glory hole at the top of a stope about 50 feet wide that extends vertically for about 80 feet; and numerous surface trenches. The property was under new ownership in 1940 (Roehm, 1940) but most of the development and production probably took place before the early 1900s.
Indication of production Yes; small
Reserve estimates None.
Production notes By 1887, the property had a 5-stamp mill and 60 tons of ore was produced from two adits. By 1904, there was a 10-stamp mill and about 1,200 tons of ore had been produced above the main adit, the No. 2 tunnel. There are no records but there certainly was some production.

Additional comments

MAS number: 0021160017.

References