. Bulletin - United States National Museum. Science. THE MINERALS OF IDAHO 273. The specific gravity of the analyzed sample was found to be (orthoclase = , Dana). A determination of alkalies in a specimen from the Trade Dollar vein gave George Steiger: Potash K20 per cent, Soda (Na20) per cent. Another specimen from the same vein in basalt gave K20, per cent. In thin section the valencianite has the characteristics of orthoclase the index of refraction, a little lower than that of quartz, helping to distinguish it from that mineral. The crystals and grains are single
. Bulletin - United States National Museum. Science. THE MINERALS OF IDAHO 273. The specific gravity of the analyzed sample was found to be (orthoclase = , Dana). A determination of alkalies in a specimen from the Trade Dollar vein gave George Steiger: Potash K20 per cent, Soda (Na20) per cent. Another specimen from the same vein in basalt gave K20, per cent. In thin section the valencianite has the characteristics of orthoclase the index of refraction, a little lower than that of quartz, helping to distinguish it from that mineral. The crystals and grains are single individuals and many of the larger ones show optical anomalies probably due to pressure. In addition to Lindgren's specimens, several collected more recently by E. L. Jones, jr., of the United States Geological Survey, have been examined. A specimen from the Blaine tunnel dump consists of a fine flat crust of white to colorless crystals of rhombic aspect reaching 7 mm. maximum diame- ter, coating a fissure in altered igneous rock. A specimen from a raise 1,300 feet from the portal of the Blaine tunnel con- sists of altered rock fragments cemented by a granular quartz-adularia aggregate con- taining finely disseminated silver sulphides and chalcopyrite. Drusy cavities in this specimen are lined with well-formed crys- tals of colorless adularia up to 5 mm. in diamater associated with small slender quartz crystals. A specimen from the ore bin of the Silver City mine consists largely of coarse granular white valencianite in- tergrown with quartz with small valencianite crystals of the usual habit in cavities. Another specimen from a tunnel dump on the south side of Long Gulch below the Blaine tunnel consists of frag- ments of altered and epidotized igneous rock cemented by quartz combs bearing curved and striated valencianite crystals up to 2 cm. in diameter. Some fluorite rests upon the valencianite. The simple habit which characterizes the cystals from most of the specimens which
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