File:Garnet-pyroxene-molybdenite-scheelite skarn (Late Cretaceous, 92 Ma; Reilly Mine, eastern side of Osgood Mountains, northern Nevada) 3 (14881921489).jpg
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| Description |
Garnet-pyroxene-molybdenite-scheelite skarn from the Cretaceous of Nevada, USA. (view under ultraviolet (UV) light; field of view ~4.6 cm across) Skarn is a contact metamorphic rock with a crystalline texture. It forms by heating and addition of elements (metasomatism) to country rock in the immediate vicinity of an igneous intrusion (batholith, stock, sill, dike, laccolith). Carbonate rock skarn is frequently called tactite. The rock shown above is an andradite-diopside skarn from Nevada having reddish-brown andradite garnets (ideally Ca3Fe2Si3O12), dark greenish diopside (a Ca-Mg pyroxene), scattered silver-colored molybdenite (molybdenum sulfide - MoS2), a little quartz (silicon dioxide - SiO2), and whitish-colored scheelite (calcium tungstate - CaWO4). The molybdenite content is high enough for this rock to qualify as a molybdenum ore. All of the above-cited minerals are not visible in the above photo, except for scheelite. The scheelite in this rock specimen is whitish-colored in normal light, but fluoresces bright blue under ultraviolet (UV) light. The other minerals do not fluoresce. Geology - contact metamorphosed limestones of the Comus Formation (Upper Cambrian-Lower Ordovician) against the Osgood Mountain Stock, an early Late Cretaceous (92 Ma) granodiorite intrusion. The garnet-rich skarn zone around the Osgood Mountain Stock is moderately rich in tungsten (W) and occasional molybdenum (Mo). Locality - Reilly Mine (section 9, T38N, R42E), Potosi District, eastern side of the Osgood Mountains (Osgood Range), eastern Humboldt County, northern Nevada, USA (= approximately 41° 11’ 21” North, 117° 15’ 03” West) |
| Date | |
| Source | Garnet-pyroxene-molybdenite-scheelite skarn (Late Cretaceous, 92 Ma; Reilly Mine, eastern side of Osgood Mountains, northern Nevada) 3 |
| Author | James St. John |
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This image was originally posted to Flickr by James St. John at https://flickr.com/photos/47445767@N05/14881921489. It was reviewed on 1 December 2019 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
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| Date/Time | Thumbnail | Dimensions | User | Comment | |
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| current | 09:06, 1 December 2019 | | 3,008 × 2,000 (1.91 MB) | Ser Amantio di Nicolao (talk | contribs) | Transferred from Flickr via #flickr2commons |
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