File:Blueschist with fluorescing benitoite-neptunite-joaquinite-natrolite vein (Franciscan Complex, Jurassic-Cretaceous; Middle Miocene vein mineralization, 12 Ma; Dallas Gem Mine, California, USA) (25608538391).jpg
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Fluorescing benitoite crystals from California, USA. (public display, Carnegie Museum of Natural History, Pittsburgh, Pennsylvania, USA) The bright blue-glowing crystals shown above are benitoite, a very rare barium titanium silicate mineral (BaTiSi3O9) known principally from San Benito County, California, USA. Large, gem-quality crystals that have been cut, faceted, and polished have the “fire” of diamond (~same index of refraction), but have a lovely deep blue color (<a href="http://www.jewelryexpert.com/catalog/graphics/Fancy-Trillium-Benitoite-1.gif" rel="nofollow">www.jewelryexpert.com/catalog/graphics/Fancy-Trillium-Ben...</a>). Benitoite is a metamorphic mineral. Its principal occurrence is in California, where polymineralic veins have intruded a blueschist body between serpentinites and greenstones of the Franciscan Formation. The Franciscan Fm. is a widespread, heterolithic unit of Jurassic-Cretaceous age in the Coast Ranges of western California. The vein mineralization age is late Middle Miocene (12 m.y.). Four minerals are commonly found in these veins: benitoite (blue), neptunite (blackish - Na2KLi(Fe,Mn)2Ti2Si8O24), natrolite (white - Na2Al2Si3O10·2H2O), and joaquinite (orangish-brown - Ba2NaCe2FeTi2Si8O26(OH,F)·H2O). The natrolite portion is acid-soluble. Nicely crystalline rock faces like the one shown above are produced by acid etching the natrolite-dominated veins. After acid treatment, the other minerals stand out in relief. Benitoite crystals glow a bright blue color while under black light - ultraviolet light (UV). Why do some minerals fluoresce under UV light? When short-wavelength UV radiation, long-wavelength UV radiation, or x-rays bombard atoms, electron excitation occurs. The electrons do not remain in an energetically excited state. They quickly give off energy and resume their normal energy levels. If the electron energy release is in the visible spectrum of light, a mineral glows, or fluoresces. Stratigraphy of blueschist host rock: Franciscan Complex, Jurassic-Cretaceous Age of benitoite-bearing vein mineralization: Middle Miocene, 12 Ma Locality: Dallas Gem Mine (a.k.a. Benitoite Gem Mine), near Santa Rita peak, southeast of New Idria, far-southeastern San Benito County, California, USA (~36° 20’ 10” North latitude, ~120° 36’ 19” West longitude) |
| Date | 30 January 2011 |
| Source | Blueschist with fluorescing benitoite-neptunite-joaquinite-natrolite vein (Franciscan Complex, Jurassic-Cretaceous; Middle Miocene vein mineralization, 12 Ma; Dallas Gem Mine, California, USA) |
| Author | James St. John |
| Permission (Reusing this file) |
  This file is licensed under the Creative Commons Attribution 2.0 Generic license.
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This image was originally posted to Flickr by James St. John at https://flickr.com/photos/47445767@N05/25608538391 (archive). It was reviewed on 4 November 2019 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
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| current | 14:42, 4 November 2019 | | 3,596 × 2,420 (3.22 MB) | Ainz Ooal Gown (talk | contribs) | Transferred from Flickr via #flickr2commons |
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