Rush and Brown

Mine, Active

Commodities and mineralogy

Main commodities Ag; Au; Cu; Fe
Ore minerals chalcopyrite; pyrite; pyrrhotite
Gangue minerals magnetite

Geographic location

Quadrangle map, 1:250,000-scale CR
Quadrangle map, 1:63,360-scale C-2
Latitude 55.62561
Longitude -132.58803
Nearby scientific data Find additional scientific data near this location
Location and accuracy The main shaft of the Rush and Brown Mine is marked by name on the USGS 1:63,360-scale topographic map; it is about 0.2 mile southeast of the center of section 18, T. 72 S., R 84 E, The extensive workings of the Rush and Brown are shown on plates 19 and 20 of Warner and others (1961).

Geologic setting

Geologic description

The rocks in the vicinity of the Rush and Brown Mine are mostly greenstone (probably metamorphosed andesite) and minor sedimentary rocks. They are part of the Descon Formation of Silurian and Ordovician age (Sainsbury, 1961; Eberlein and others, 1983; Brew, 1996). No limestone or marble is present in the mine but tactites are developed near a large magnetite ore body.
The mine has two types of deposits: a mass of magnetite and sulfide veins (Warner and others, 1961). The magnetite ore body consists almost entirely of magnetite with minor chalcopyrite and pyrite along tiny fractures in the magnetite. Aside from a few pillars, the magnetite ore body was almost entirely mined out from a glory hole. Originally it was about 160 feet long, 40-50 feet thick, and about 100 feet deep. Some additional magnetite-rich material is exposed but it had too low a copper content to mine.
The main sulfide vein, which extends from the surface to the 500-foot level, was the principal source of the ore. It strikes about N60E at the surface, about N55E at the 200-foot level, and nearly east at the 400-foot and 450-foot levels. The vein dips 60SE at the surface, 55SE at the 200-foot level, and 30E at the 500-foot level. In places the stopes were 14 feet wide. As described by Mertie (1921), the ore body in the vein consisted of chalcopyrite with some pyrite and pyrrhotite, that occurred in lenses and reticulated veins and veinlets in sheared rock. The gangue is mostly crushed country rock. The ore bodies extended about 400 feet horizontally from the surface to the deepest level of workings at the 500-foot level. There are also several smaller, similar veins nearby that have not been mined.
The Rush and Brown Mine was discovered in 1904 and ore was shipped almost continuously from 1906 to 1923 by the Alaska Copper Company and U.S. Rush, the owner of the mine. The mine closed in 1923 for lack of a convenient smelter to process the ore and due to low copper prices. In 1929, a subsidiary of the Consolidated Mining and Smelting Company optioned the mine and shipped a small amount of ore. The mine consists of 6 levels and a glory hole. Plate 19 of Warner and others (1961) is a map of the workings. The U.S. Bureau of Mines drilled 4 holes during World War II (Holt and others, 1948). There is a long adit, the Sawmill adit, that was driven to tap the ore body at depth. Warner and others note that the adit stopped about 175 feet short of the main vein. Maas and others (1995) indicate that the Sawmill adit was extended sometime between 1960 and the mid-1980s to intersect the main vein at about the 200-foot level; their figure 9 is a map of the extension and the stopes that were mined from it. In 1995, the Rush and Brown Mine was on claims controlled by Fox Geological Consultants, Ltd. Most of the exploration and emphasis has been at Salt Chuck (CR049), but the Rush and Brown Mine continues to be of interest.
Holt and others (1948) indicate that the main vein down to the 500-foot level produced 9,700 tons of hand-sorted ore that averaged 10.5 percent copper, 0.26 ounce of gold per ton, and 1.6 ounce of silver per ton. The magnetite ore body produced about 35,000 tons of ore that contained an average of 3.25 percent copper, 0.06 ounce of gold per ton, and 0.25 ounce of silver per ton. Maas and others (1995) give the total production of the mine as 2,160 tons of copper, 1.65 tons of silver, and 8,198 ounces of gold. The magnetite ore body was entirely mined out. The ore bodies on the main vein appear to extend undiminished in grade and size below the deepest workings at the 500 level.
Geologic map unit (-132.589694114568, 55.6252396252238)
Mineral deposit model Magnetite mass with minor chalcopyrite and pyrite and a mineralized shear (vein) with chalcopyrite and minor pyrite and pyrrhotite.
Age of mineralization Unknown; the host rocks are Silurian or Ordovician and the deposits are similar to the Cu-Fe deposits on the Kasaan Peninsula (see, for example, CR051).
Alteration of deposit Tactite developed in the magnetite ore body.

Production and reserves

Workings or exploration The Rush and Brown Mine was discovered in 1904 and ore was shipped almost continuously from 1906 to 1923 by the Alaska Copper Company and U.S. Rush, the owner of the mine. The mine closed in 1923 for lack of a convenient smelter to process the ore and due to low copper prices. In 1929, a subsidiary of the Consolidated Mining and Smelting Company optioned the mine and shipped a small amount of ore. The mine consists of 6 levels and a glory hole. Plate 19 of Warner and others (1961) is a map of the workings. The U.S. Bureau of Mines drilled 4 holes during World War II (Holt and others, 1948). There is a long adit, the Sawmill adit, that was driven to tap the the ore body at depth. Warner and others note that the adit stopped about 175 feet short of the main vein. Maas and others (1995) indicate that the Sawmill adit was extended sometime between 1960 and the mid-1980s to intersect the main vein at about the 200-foot level; their figure 9 is a map of the extension and the stopes that were mined from it. In 1995, the Rush and Brown Mine was on claims held by Fox Geological Consultants, Ltd. (Maas and others, 1995).
Indication of production Yes; medium
Reserve estimates The magnetite ore body was almost entirely mined out. The ore bodies on the main vein appear to extend undiminished in grade and size below the lowest workings at the 500 level.
Production notes Holt and others (1948) indicate that the main vein down to the 500-foot level produced 9,700 tons of hand-sorted ore that averaged 10.5 percent copper, 0.26 ounce of gold per ton, and 1.6 ounce of silver per ton. The magnetite ore body produced about 35,000 tons of ore that contained an average of 3.25 percent copper, 0.06 ounce of gold per ton, and 0.25 ounce of silver per ton. Maas and others (1995) give the total production of the mine as 2,160 tons of copper, 1.65 tons of silver, and 8,198 ounces of gold. The magnetite ore body was entirely mined out. The ore bodies on the main vein appear to extend undiminished in grade and size below the deepest workings at the 500 level.

References

MRDS Number A010127; A010128

References

Thorne, R.L., Holt, A.W., Tolonen, A.W., Wright, W.S., and Fosse, E.L., 1945, Mount Andrew iron deposit, Kasaan Peninsula, Prince of Wales Island, southeastern Alaska: Draft War Minerals Report, 42 p.
Reporters D.J. Grybeck (Applied Geology)
Last report date 5/1/2004