U.S. Geological Survey Photographic Library

Photos 5626 to 5650 of 11730.
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5626. jwdj0064.gif Sheeted vein, North Star mine, No. 3 vein, 8,600-foot level: Underground photograph of sheeted veins. Nevada County, California. 1931. Plate 10-B, U.S.Geological Survey Professional paper 194. 1940. ID. Johnston, W.D., Jr.  64
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5627. jwdj0073.gif Pinch in quartz vein from 24 to 6 inches, North Star mine, No. 2 vein, 7,200-foot level: Underground photograph of quartz veins. Nevada County, California. 1931. Plate 9-F, U.S.Geological Survey Professional paper 194. 1940. ID. Johnston, W.D., Jr.  73
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5628. jwdj0077.gif Comb and sheared quartz: thin section of upper part of comb and sheared quartz; it shows clear euhedral quartz surrounded by a dark rim of fine grained ankerite and all interstices filled with coarser-grained ankerite. The lower part of the section shows older sheared quartz with a little ankerite. Black polygons in clear quartz near top of section are pyrite. Nevada County, California. 1931. Plate 17-B, U.S.Geological Survey Professional paper 194. 1940. ID. Johnston, W.D., Jr.  77
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5629. jwdj0079.gif Vugs and comb quartz: thin section from vug, showing euhedral quartz, chlorite and carbonates. Nevada County, California. 1931. Plate 15-C, U.S.Geological Survey Professional paper 194. 1940. ID. Johnston, W.D., Jr.  79
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5630. jwdj0081.gif Comb quartz and carbonates: same section with carbonates dissolved by hydrochloric acID. The quartz shows comb structure and cavities, which existed prior to the introduction of the carbonates. North Star mine No. 2 vein, 8,600-foot level: Opposite saw-cut face of photo 82. Nevada County, California. 1931. Plate 18-A, U.S.Geological Survey Professional paper 194. 1940. ID. Johnston, W.D., Jr.  81
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5631. jwdj0082.gif Comb quartz and carbonates: polished section of vein composed of quartz and carbonates, North Star mine No. 2 vein, 8,600-foot level: Opposite saw-cut face of photo 81. Nevada County, California. 1931. Plate 18-A, U.S.Geological Survey Professional paper 194. 1940. ID. Johnston, W.D., Jr.  82
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5632. jwdj0088.gif Photographs of ore: Polished slab showing sheared quartz with later calcite, the black areas are indurated gouge; North Star mine, New York Hill vein, 3,400-foot level. Nevada County, California. 1931. Plate 11-B, U.S.Geological Survey Professional paper 194. 1940. ID. Johnston, W.D., Jr.  88
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5633. jwdj0089.gif Photographs of ore: Polished slab showing broken pyrite in vein quartz, North Star mine, No. 1 vein, 8,200-foot level. Nevada County, California. 1931. Plate 11-A, U.S.Geological Survey Professional paper 194. 1940. ID. Johnston, W.D., Jr.  89
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5634. jwdj0090.gif Photographs of ore: polished slab showing sheared quartz with carbonate, cement; North Star mine, No. 3 vein, 9,000-foot level. Nevada County, California. 1931. Plate 11-C, U.S.Geological Survey Professional paper 194. 1940. ID. Johnston, W.D., Jr.  90
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5635. jwdj0092.gif Polished slab of granodiorite showing sheeted zone of carbonate veinlets, North Star mine, No. 1 vein, 7,200-foot level: Underground photograph of sheeted veins. Nevada County, California. 1931. Plate 10-A, U.S.Geological Survey Professional paper 194. 1940. ID. Johnston, W.D., Jr.  92
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5636. jwdj0095.gif Vugs and comb quartz: Polished slab from vug, euhedral quartz crystals are coated with white ankerite. The vug is filled with a dark-green mixture of chlorite and mechanically ground quartz in a matrix of carbonates. Nevada County, California. 1931. Plate 15-B, U.S.Geological Survey Professional paper 194. 1940. ID. Johnston, W.D., Jr.  95
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5637. jwdj0097.gif Strong Walls in granodiorite with interstitial breccia zone: Empire mine, 5,000-foot level. Nevada County, California. 1931. Plate 7-A, U.S.Geological Survey Professional paper 194. 1940. ID. Johnston, W.D., Jr.  97
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5638. jwdj0113.gif Split in quartz vein with badly shattered septum and many cross veinlets. The granodiorite inclusions are probably replaced by carbonates and sercicite. The scale is 6 inches long: North Star mine, No. 2 vein, 6,600-foot level: Underground photograph of sheeted veins. Nevada County, California. 1931. Plate 10-E, U.S.Geological Survey Professional paper 194. 1940. ID. Johnston, W.D., Jr. 113
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5639. jwdj0221.gif Mineralogy of the veins: Polished slab showing scheelite and quartz vein filling: Union Hill mine. Nevada County, California. 1931. Plate 12-A, U.S.Geological Survey Professional paper 194. 1940. ID. Johnston, W.D., Jr. 221
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5640. jwdj0298.gif Details of vug lining: thin section of vug filling; euhedral quartz is surrounded by a vein of ankerite (dark) and a vein of smaller quartz combs (light). At that stage the vug lining was disturbed, and some of the euhedral quartz crystals were broken. Finally a mixture of chlorite and mechanically ground quartz cemented by ankerite filled the entire vug and formed a matrix around the earlier combs, North Star mine, No. 2 vein, 6,300-foot level. Plain light. Nevada County, California. 1931. Plate 16-A, U.S.Geological Survey Professional paper 194. 1940. ID. Johnston, W.D., Jr. 298
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5641. jwdj0299.gif Details of vug lining: thin section of vug filling; euhedral quartz is surrounded by a vein of ankerite (dark) and a vein of smaller quartz combs (light). At that stage the vug lining was disturbed, and some of the euhedral quartz crystals were broken. Finally a mixture of chlorite and mechanically ground quartz cemented by ankerite filled the entire vug and formed a matrix around the earlier combs, North Star mine, No. 2 vein, 6,300-foot level. Crossed nicols. Nevada County, California. 1931. Plate 16-B, U.S.Geological Survey Professional paper 194. 1940. ID. Johnston, W.D., Jr. 299
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5642. jwdj0302.gif 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. ID. Johnston, W.D., Jr. 302
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5643. jwdj0303.gif Photomicrograph of brecciated quartz: cemented by chalcedony, in the large quartz area at the top center are two small vugs lined with clear opal. Golden Center mine, Sleep vein, 500-foot level. One nicol. Nevada County, California. 1931. Plate 20-B, U.S.Geological Survey Professional paper 194. 1940. ID. Johnston, W.D., Jr. 303
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5644. jwdj0304.gif Photomicrograph showing zoned enclosures and vacuoles: quartz with marginal zones of vacuoles parallel to prism faces. In the interior of the crystals the lines of vacuoles are independent of crystallographic direction. In the upper part of the section sercicite is replacing quartz. North Star mine, No. 1 shaft, below 7,850-foot station. Plain light. Nevada County, California. 1931. Plate 21-B, U.S.Geological Survey Professional paper 194. 1940. ID. Johnston, W.D., Jr. 304
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5645. jwdj0306.gif Photomicrograph of brecciated quartz: cemented by ankerite, the black dots in the clear quartz are vacuoles. Empire mine, Newmont vein, 3,800-foot level: One nicol. Nevada County, California. 1931. Plate 20-A, U.S.Geological Survey Professional paper 194. 1940. ID. Johnston, W.D., Jr. 306
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5646. jwdj0307.gif Vacuoles and phantom veinlets: vacuoles in vein quartz with occluded liquid containing gas bubbles. North Star mine, No. 2 vein, 6,900-foot level. Nevada County, California. 1931. Plate 22-A, U.S.Geological Survey Professional paper 194. 1940. ID. Johnston, W.D., Jr. 307
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5647. jwdj0308.gif Vacuoles and phantom veinlets: another thin section from the same specimen as photo 307; a negative crystal appears in the center. Nevada County, California. 1931. Plate 22- B, U.S.Geological Survey Professional paper 194. 1940. ID. Johnston, W.D., Jr. 308
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5648. jwdj0309.gif Photomicrographs of sheared quartz: comb quartz granulated along the vein wall. Fine- grained material at top of section is ankerite. Thin section shows the development of sheared textures from comb quartz. North Star mine, No. 3 vein, 9,000 foot-level. Crossed nicols. Nevada County, California. 1931. Plate 19-D, U.S.Geological Survey Professional paper 194. 1940. ID. Johnston, W.D., Jr. 309
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5649. jwdj0310.gif Photomicrograph showing zoned enclosures and vacuoles: ankerite veinlets cutting small quartz vein and extending into the wall rock. Empire mine, 2,700-foot level. Plain light. Nevada County, California. 1931. Plate 21-A, U.S.Geological Survey Professional paper 194. 1940. ID. Johnston, W.D., Jr. 310
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5650. jwdj0311.gif Photomicrographs of sheared quartz: irregular granulation zones, note strain lines in the larger quartz grains. Empire mine 4,000-foot level. Crossed nicols. Nevada County, California. 1931. Plate 19-B, U.S.Geological Survey Professional paper 194. 1940. ID. Johnston, W.D., Jr. 311
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