Base de données des minéraux luminescents 

SCHEELITE

Formule chimique: CaWO₄

Famille: Tungstates, Molybdates

Statut: IMA-GP

Système cristallin : Quadratique

Minéral de vitrine: OUI

Noms associés (variétés luminescentes, noms discrédités, synonymes etc.): cuproscheelite,  molybdoscheelite, 

Luminescence:

Photo en lumière du jour

SCHEELITE, China
Photo and Copyright: James Hamblen
Site of the author
Used with permission of the author

Photo Ondes Courtes (254nm)

SCHEELITE under UVSW
Photo and Copyright: James Hamblen
Site of the author
Used with permission of the author

Galerie de photos:

  
  Accès à la galerie complète (34 images au total)

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Phosphorescence (au sens commun du terme) observable à l'oeil nu:

Pas de données

Thermoluminescence: OUI

Commentaires:

Une fine couche de scheelite recouvre parfois la wolframite donnant l'impression que celle ci est fluorescente.

Les tungstates de calcium, de strontium, de magnésium et de zinc, et les molybdates de calcium sont connus pour leur luminescence lors de l'excitation par les rayons cathodiques ou les rayons ultraviolets à ondes courtes. Il est communément admis que cette luminescence est caractéristique des groupes  tungstate et  molybdates. La raison pour laquelle d'autres tungstates et molybdates s'avèrent non luminescents est probablement un effet de la température (temperature quenching) (voir l'article de Nature par F. A. Kröger publié en 1947 dans la bibliographie).

Activateur(s) et spectre(s):

Activateur(s): WO₄^2-, Sm³⁺,  Eu³⁺,  Dy³⁺,  Ho³⁺,  Er³⁺,  Tb³⁺,  Pr³⁺,  Nd³⁺,  Yb³⁺,  Tm³⁺,  

Pics dans le spectre (nm):

WO₄^2-: Broad band centered at 425 - 435nm  (Lifetime: 9μs @ 405nm)
Tb³⁺: 439nm
Dy³⁺: 488, 575nm
Sm³⁺: 609, 647nm
Pr³⁺: 607nm

Spectrum: Michael Gaft, Petah Tikva, Israel. Plot: Institute of Mineralogy, University of Vienna, Austria, with permission of the authors.

Galerie de spectres:

  
  Accès à la galerie complète (10 images au total)

Commentaires sur les spectres et les activateurs (*):

Scheelite is characterized by broad luminescent bands centered at 425 - 435 nm (blue emission) of intrinsic activator (WO₄)^2- groups and impurity (MoO₄)^2- groups.

 Those broad bands are attributed to an intrinsic slight distortion of the [WO₄]/ [MoO₄] tetrahedral group. [WO₄] lifetime: 9μs (@ 405nm).

Such strong bands prevent in many cases the detection of lines of rare-earth elements, especially Tm, Er and Ho, which have weak luminescence in the corresponding spectral range.

Yet, scheelite incorporates often tens to thousands of ppm RRE in substitution for Ca giving sometimes typical peaks in the fluorescence spectrum. Visible peaks in relation with the presence of REE: 488 et 575 (Dy³⁺), 609 et 647 (Sm³⁺), 439 (Tb³⁺) et 607 (Pr³⁺). But the lines of certain REE may be hidden by stronger luminescence of others REE. For example, the luminescence of Pr3+ is difficult to detect because its radiative transitions are hidden by the lines of Sm3+, Dy3+ and Nd3+, the luminescence of Tm3+ is concealed by Tb3+ and so on.

The pegmatitic and hydrothermel scheelite  shows the lines of Erbium and Terbium, while scheelite occurrences related to eruptive complex and sulfide ore shows dominantly the lines of the REE of the Cerium group.

Under cw laser excitation at 532 several narrow lines have been found in red and IR part of the spectrum connected with Nd³⁺ and possibly Sm³⁺ centers.

Green emission due to (MoO₄)^2-(Tarashchan) or possibly Pb (Blasse).

The color of the fluorescence of scheelite gives an idea of the unwilled presence of molybdenium in the ore. Concentrate of scheelite not penalized for molybdenium have a distinct blue fluorescence color. Those that fluoresce white are borderline  and contain roughly 0,35% to 1% of Mo. And scheelite that fluoresces distinctly yellow contains more than 1% corresponding to a transition to powellite. Higher than 4,8%, the yellow fluorescence color stays unchanged and cannot anymore be used as an indication of the percentage of Mo. Using this property, a method was  developped by R.S. Canon jr. (1942) while studying tungsten deposits in the seven Devils mining district of Idaho. A serie of finely powdered synthetic preparation or natural ore of known composition are permanently mounted in circular areas on a black card, being placed in order of increasing molybdenium content. There are twelve standard values on the card: 0,05, 0,19, 0,33, 0,48, 0,72, 0,96, 1,4, 2,4, 3,4, and 4,8% plus a pure calcium molybdate (48% Mo). Alternating with the covered circle are circular holes of the same size. The card is used by placing a hole over a powdered sample of the scheelite ore to be tested and comparing the fluorescence color of the sample with those of the adjacent standards. The sample will be found to have a fluorescence color according or between two standards and hence the approximate composition could be defined.

(*)Les commentaires sur les spectres sont uniquement rédigés en Anglais

Meilleure(s) localité(s) pour la fluorescence (*):

• Pingwu beryl mine, Huya township, Mt Xuebaoding, Pingwu Co., Mianyang Prefecture, Sichuan Province, China;
• Yaogangxian Mine, Yaogangxian W-Sn ore field, Yizhang Co., Chenzhou Prefecture, Hunan Province, China;
• Huanggang Fe-Sn deposit, Hexigten Banner, Ulanhad League, Inner Mongolia Autonomous Region, China
• Mt. Xuebaoding, Sichuan Province, China (bright red MW);
• Xuebaoding Mountain, near Pingwu, Sichuan Province, China (bluish-white SW, orange LW);
• Gharmung area, Skardu District, Gilgit-Baltistan, Pakistan;
• Pari, Kharmang District, Gilgit-Baltistan, Pakistan;
• Tae Hwa Mine, Neungam-ri, Angseong-myeon, Chungju, Chungcheongbukdo, South Korea;
• Mundo Nuevo, Huamachuco, Sanchez Carrion Province, La Libertad, Peru;
• Morro Velho mine, Nova Lima, Minas Gerais, Brazil;
• Guadalupana Mine, Sierra del Chivato, Santa Cruz, Santa Cruz Municipality, Sonora, Mexico (weak Brownish-greenish SW);
• Cínovec / Zinnwald, Erzgebirge; Krusné Hory Mts, Germany & Czech Republic;
• Wolfram Bergbau und Hütten AG Mine (7 km S of Mittersill) Western ore field, Scheelite deposit, Felben valley, Hohe Tauern, Salzburg, Austria;
• Långban, Filipstad, Värmland, Sweden;
• Camp Bird Mine, Camp Bird, Sneffels District, Ouray, Ouray District, San Juan Mts, Ouray Co., Colorado, USA (blue SW, white LW);
• Kernville, Cove Mining District, Kern Co., California, USA;
• Route 20 construction site, Northborough, Worcester Co., Massachusetts, USA;
• Trumbull, Fairfield County, Connecticut, USA;
• Franklin Mining District, Sussex Co., New Jersey, USA (MW+SW white to cream);
• Carrock Mine, Mungrisdale, Eden, Cumbria, England, UK;
• Mont Chemin mining district, Martigny, Valais, Switzerland;
• Virgen de la Encina Mine, Salas de los Barrios, Ponferrada, León, Castile and Leon, Spain;
• Conchita Mine, Estepona, Málaga, Andalusia, Spain;
• Traversella Mine, Traversella, Metropolitan City of Turin, Piedmont, Italy;
• Kimmeria, Xanthi, East Macedonia and Thrace, Greece;
• Western ore field, Mittersill Scheelite deposit, Mittersill, Zell am See District, Salzburg, Austria;

(*)Les données ne sont pas exhaustives et sont limitées à quelques localités remarquables pour la fluorescence

Référence bibliographique pour la luminescence:

• The Henkel Glossary of Fluorescent Minerals, Dr. Gerhard Henkel, Published by the FMS, 1989 ,
• Fluorescence: Gems and Minerals Under Ultraviolet Light, Manuel Robbins, 1994, Geoscience Press, ISBN 0-945005-13-X ,
• The World of Fluorescent Minerals, Stuart Schneider, Schiffer Publishing, 2006, ISBN 0-7643-2544-2 ,
• Collecting Fluorescent Minerals, Stuart Schneider, Schiffer Publishing, 2004, ISBN 0-7643-2091-2 ,
• Luminescence Spectroscopy of Minerals and Materials, M. Gaft, R. Reisfeld, G. Panczer, Springer Editor, ISBN: 10 3-540-21918-8 ,
• Luminescent Spectra of Minerals, Boris S. Gorobets and Alexandre A. Rogojine, Moscow, 2002 ,
• Ultraviolet Light and Fluorescent Minerals, Th. Warren, S. Gleason, R. Bostwick, et E. Verbeek, 1995, ISBN 0-9635098-0-2 ,
• Mt St Hilaire Website: http://www.saint-hilaire.ca ,
• Luminescenza nel regno minerale, Guido Mazzoleni, fotografia Roberto Appiani, Libri Sandit, 2010, ISBN 978-88-95990-63-7 ,
• Handbook of Fluorescent Gems and Minerals, a practical guide for the gem and mineral collector, Jack de Ment, 1949 ,

Référence pour la luminescence sur internet:

Référence minéralogique sur internet:

  http://www.mindat.org/show.php?name=Scheelite

  http://webmineral.com/data/Scheelite.shtml

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