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Opal-CT

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Dallet, Puy-de-Dôme, Auvergne, France
© Rémi BORNET

Show Opal-CT Photos (23)



Formula:
SiO
 
2
 · nH
 
2
O
A variety of Opal

Consists of packed microscopic (150-300 nm) spheres made up of tiny microcrystalline blades of Cristobalite and/or Tridymite, with water content as high as 10 wt%.

In opal-CT there is the beginning of the formation of domains of short-range ordering which have arrangements of silica and water that is similar to the arrangement of atoms in cristobalite and tridymite. The X-ray powder diffraction pattern is distinguished by the presence of a well-defined broad hump with a satellite peak on the low-angle side and a possible shoulder on the high-angle side. A second weaker peak at a higher angle is also present. The ordered regions occur in a matrix of disordered opal, but it is difficult at this time to suggest that the system is two-phase. There is no evidence yet to show that the ordered domains have lost their water and are anhydrous. The fraction of the material which is composed of ordered domains is very small. The term micro-crystalline should not be applied to this material.

Classification of Opal-CT

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Chemical Properties of Opal-CT

Formula:
SiO
 
2
 · nH
 
2
O
All elements listed in formula:H, O, Si

Other Names for Opal-CT

Synonyms:
Lussatite
Other Languages:

Other Information

Health Warning:No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

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    • Localities for Opal-CT

    The map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
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    (TL) indicates type locality. ? indicates mineral may be doubtful at this locality. All other localities listed without reference should be considered as uncertain and unproven until references can be found.
    Austria
     
    • Lower Austria
      • Waldviertel
        • Brunn an der Wild
          • Atzelsdorf
    		Pristacz, H., jun., Kolitsch, U., Löffler, E., Knobloch, G., Prayer, A. & Thinschmidt, A. (2011): 1696) Calcit, Natrojarosit, Palygorskit, Pyrit, Siderit und andere Mineralien aus dem Marmorbruch Atzelsdorf, Brunn an der Wild, Waldviertel. Pp. 160-161 in Niedermayr, G. et al. (2011): Neue Mineralfunde aus Österreich LX. Carinthia II, 201./121., 135-186.
    • Styria
      • Bad Radkersburg
        • Klöch
    		Taucher, J. & Hollerer, C. E. (1998): Minerale eines Si- und Al-reichen Xenoliths aus dem Basaltsteinbruch von Klöch, Nördlicher Bruch, (Steiermark, Österreich). Mitt. naturwiss. Ver. Steiermark 128, 21-42.
      • Murau
        • Katsch an der Mur
    		http://www.markasit070752.ws24.cc/text_62520295_60708465_19667850_deutsch.html
    France
     
    • Aquitaine
      • Lot-et-Garonne
    		Econ Geol (1989) 84:1541-1556
    • Auvergne
      • Puy-de-Dôme
        • Clermont-Ferrand
    		Remi Bornet Collection
    Remi Bornet Collection
    Aimé Rudel : "Curiosités Géologiques d'Auvergne et du Velay", Editions Volcans, 1970
        • Lempdes
    		Remi Bornet Collection
    Remi Bornet Collection
    Mallard, E., 1890, Bull. Soc. Min., v13, p. 63
    Remi Bornet Collection
    Remi Bornet Collection
    Mexico
     
    • Coahuila
      • Mun. de Cuatrociénegas
        • Cuatro Ciénegas (Cuatrociénegas de Carranza; Venustiano Carranza)
          • Limestone caves
    		Forti, P. et al. (2006): ACTA CARSOLOGICA 35/1, 79–98.
    Pacific Ocean
     
    • South California Borderland
    		Hein, J.R., Reid, J.A., Conrad, T.A., Dunham, R.E., Clague, D.A., Schulz, M.S., and Davis, A.S. (2010): USGS Open-File Report 10-1069
    Peru
     
    • Cajamarca Department
      • Cajamarca Province
        • Cajamarca
    		Dill, H.G., Bosse, H.-R., Henning, K.-H., Fricke, A., and Ahrendt, H. (1997): Mineralium Deposita 32, 149-163.
    Turkey
     
    • Aegean Region
      • Kütahya Province
        • Pazarla
    		Mutlu, H., Sariiz, K., and Kadir, S. (2005): Ore Geology Reviews 26, 39-50.
    • Central Anatolia Region
      • Ankara Province
    		Temel, A., Akdag, N., and Varol, E. (2010): Goldschmidt Conference Abstracts 2010.
    USA
     
    • Colorado
      • Mineral Co.
        • Creede District
    		Minerals of Colorado (1997) E.B. Eckels
    Mineral and/or Locality
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    Copyright © Jolyon Ralph and Ida Chau 1993-2011. Site Map. Locality, mineral & photograph data are the copyright of the individuals who submitted them. Further information contact the Site hosted & developed by Jolyon Ralph. Mindat.org is an online information resource dedicated to providing free mineralogical information to all. Mindat relies on the contributions of hundreds of members and supporters. Mindat does not offer minerals for sale. If you would like to add information to improve the quality of our database, then click here to register.
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