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Electrum showing crystal outlines associated with quartz and sulphides. The argentite was very probably formed by the replacement of galena, but all the other minerals are believed to be alpha hypo gene. Photomicrograph of polished surface of ore from 1,260- foot level, Murray vein, Tonopah Extension mine. Nye County, Nevada. 1915. Plate 5- B, with graphics, in U.S. Geological Survey. Professional paper 104. 1918.
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Album caption and index card: Photomicrograph of gold-tungsten ore from Keklonga mine, Magnolia district. Sylvanite (s) in vuggy quartz (q3) which contains a little pyrite (py). Quartz (q3) and ferberite (fe) cut in early quartz. Boulder County, Colorado. Notes: Published as figure LXXIV-B in U.S.Geological Survey. Professional Paper 223. 1950.
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Photomicrograph of polished section. Large grains of early pyrite coated with marcasite. Sphalerite and chalcopyrite fill cavity between pyrite grains. X 175, Lucky Strike mine. Summit County, Colorado. Circa 1963. Published in US Geological Survey Professional Paper 652, figure 18-B. 1971.
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Photomicrograph of vein rock shown in photo 37, with plain light, showing orthoclase, or, fractured and veined by quartz q. Bartow County, Georgia. Circa 1944. Plate 12-C, in U.S.Geological Survey Professional paper 224. 1950.
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Photomicrograph of polished sections of ore: supergene gold veinlets deposited in fractures in hessite. Surface etched with #1:1 HNO3; large area of white mineral unaffected by acid is coloradoite. Gangue is quartz; reflected light 157 x. Eagle Pass mine. Photo by F.W. Galbraith. La Plata County, Colorado. Circa 1936. Plate 12-D, in U.S.Geological Survey Professional paper 219. 1949.
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Photomicrograph of pseudomorphic quartz and adularia after calcite; from Pick and Shovel mine, 100-foot level. Example of cellular, drusy, radial, and bladed structures characteristic of the Jarbidge veins. Magnified 25 diameters. Elko County, Nevada. 1910. Plate 9 in U.S. Geological Survey. Bulletin 497. 1912.
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Photomicrograph showing zoned enclosures and vacuoles: euhedral quartz surrounded by fine-grained ankerite and chlorite. Empire mine, 7,000-foot level. Plain light. Nevada County, California. 1931. Plate 21-D, U.S.Geological Survey Professional paper 194. 1940.
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Photomicrograph of polished sections of ore: hypogene chalcopyrite replaced by supergene bornite; Chalcopyrite, bornite; reflected light 175 x.
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Photomicrograph of polished sections of ore. Boxwork structure of magnetite; chalcopyrite has filed in boxwork and veinlet of pyrite cuts magnetite. La Plata County, Colorado. 1936.
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Photomicrograph of polished sections of ore: Intergrowth of krennerite and native tellurium; specimen etched with concentrated HNO3; cleavage pattern produced by etching is characteristic of krennerite. Gangue is quartz; reflected light 180 x. Gold King mine. Photo by F.W. Galbraith. La Plata County, Colorado. Circa 1936. Plate 11-A, in U.S.Geological Survey Professional paper 219. 1949.
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Possible presence of hydrocarbons (?) in Nanushuk Group rocks. Migration apparently occurred during or after compaction of the sandstones. Possible hydrocarbon (?) migration is facilitated along solution seams probably formed during compaction. Sample 78ACh34, Marmot syncline; magnification, 2.5 x 10, photomicrograph. Central North Slope, Alaska. Published as Figure 51A in U.S. Geological Survey. Bulletin 1614. 1985.
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Photomicrograph of polished sections of ore: subgraphic pattern of calaverite and sylvanite in hessite, Calaverite, sylvanite and hessite. These textures may indicate replacement of hessite by gold tellurides, but owing to its rarity, such replacement is not believed to be important in La Plata ores. Reflected light 250 x. Gold King mine. Photo by F.W. Galbraith. La Plata County, Colorado. Circa 1936. Plate 10-D, in U.S.Geological Survey Professional paper 219. 1949.
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Partial replacement of galena by fine aggregate of a light-colored carbonate, argentite and some chalcopyrite; there has been a slight replacement of the quartz. Photomicrograph of polished surface of ore from Favorite vein, Tonopah-Belmont mine, depth uncertain. Nye County, Nevada. 1915. Plate 9-A in U.S. Geological Survey. Professional paper 104. 1918.
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Peripheral replacement of galena by an association of argentite and electrum (stippled); note the smoothness of the galena border in passing from contact with argentite to contact with electrum. Photomicrograph of polished surface of ore from 1,250-foot level Murray vein, Tonopah Extension mine. Nye County, Nevada. 1915. Plate 9-B in U.S. Geological Survey. Professional paper 104. 1918.
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Replacement of galena by polybasite; between these two minerals occur narrow bands of an unidentified transition mineral (not visible in the picture), and the very narrow light colored bands that mark the initiation of the replacement process along the contacts between galena crystals consist of this mineral. Photomicrograph of polished surface of ore from Favorite vein, Tonopah-Belmont mine, depth uncertain. Nye County, Nevada. 1915. Plate 7-B, with graphics, in U.S. Geological Survey. Professional paper 104. 1918.
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Possible presence of hydrocarbons (?) in Nanushuk Group rocks. Migration apparently occurred during or after compaction of the sandstones. Possible hydrocarbon (?) migration into intergranular pore spaces and into a grain cracked by compaction. Dissolution pore (P) unfilled by hydrocarbon indicates that migration may have occurred prior to creation of dissolution porosity. Sample 78ACh25, Marmot syncline; magnification, 2.5 x 10, photomicrograph. Central North Slope, Alaska. Published as Figure 51B in U.S. Geoloqical Survey. Bulletin 1614. 1985.
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Transition from areas wholly galena into areas that are mainly galena with some carbonate (rough dark gray) and argentite and finally into areas that are mainly carbonate with some argentite, galena, chalcopyrite, and electrum, named in order of abundance; photomicrograph of polished surface of ore from 1,000-foot level, Favorite vein, Tonopah-Belmont mine. Nye County, Nevada. 1915. Plate 7-A, with graphics, in U.S. Geological Survey. Professional paper 104. 1918.
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Photomicrograph of vein rock shown in photo 37, with crossed nicols, showing strain twinning in orthoclase and strain shadows in quartz. Bartow County, Georgia. Circa 1944. Plate 12-D, in U.S.Geological Survey Professional paper 224. 1950.
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Polybasite (light gray) with bladelike outlines, inclosed by pyrargyrite (white); the dark gray is quartz. The polybasite has been made visible by brief treatment with mercuric chloride solution. Photomicrograph of polished surface of ore, Tonopah Extension mine, exact location uncertain. Nye County, Nevada. 1915. Plate 4-B in U.S. Geological Survey. Professional paper 104. 1918.
    map background search result map search result map Photomicrograph showing zoned enclosures and vacuoles, Empire mine. Nevada County, California. 1931. Photomicrograph of gold-tungsten ore from Keklonga mine. Boulder County, Colorado. 1932. Photomicrograph showing zoned enclosures and vacuoles, Empire mine. Nevada County, California. 1931. Photomicrograph of gold-tungsten ore from Keklonga mine. Boulder County, Colorado. 1932.