Database of luminescent minerals 

SCHEELITE

Chemical formula: CaWO₄

Family: Tungstates, Molybdates

Status: IMA-GP

Crystal system : Tetragonal

Display mineral: OUI

Associated names (luminescent varieties, discredited names, synonyms, etc.): cuproscheelite,  molybdoscheelite, 

Luminescence:

Daylight picture

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

Shortwave (254nm) picture

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

Pictures Galery:

  
  Go to the galery (34 pictures)

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Phosphorescence (in the common sense of the term) observable with the naked eye:

No data

Thermoluminescence: OUI

Comments:

A very thin  coating of SCHEELITE on WOLFRAMITE makes it glow and give the impression that this mineral is luminescent.

The tungstates of calcium, strontium, magnesium and zinc, and the molybdates of calcium are known to show luminescence upon excitation by cathode rays or short-wave ultra-violet radiation. It is commonly assumed that this luminescence is characteristic of the tungstate and molybdate groups. The reason why other tungstates and molybdates are found to be non-luminescent is probably the temperature-quenching (see Nature article by F.  A. Kröger in 1947 in the bibliography).

Activator(s) and spectrum:

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

Peaks in the spectrum (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.

Spectrum Galery:

  
  Go to the galery (10 spectra)

Comments on spectrum and activators:

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.

Best localities for 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;

(*)The data are not exhaustive and are limited to a few remarkable localities for fluorescence

Bibliographic reference for 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 ,

Reference for luminescence on the Internet:

Mineralogical reference on the Internet:

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

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

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