Abstract

The Sunshine Mine, Coeur d'Alene district, Idaho, is the leading silver mine in the United States. The vein is of the fissure type common to the district and is located on the north limb of the Big Creek Anticline. The deposit resembles Lindgren's "galena-tetrahedrite-siderite" type, of which the Wood River, Idaho, ores are representative. The important gangue minerals are siderite and quartz. Tetrahedrite is the silver-bearing mineral, but polished surfaces revealed no silver minerals in it. Presumably the silver is present as an isomorphous constituent of the tetrahedrite. The paragenesis is in keeping with the order of mineral deposition in silver deposits of this type. Pyrite was the earliest sulphide, followed by arsenopyrite, tetrahedrite, galena and chalcopyrite. The development of bournonite is common where the galena is in contact with the tetrahedrite.

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