Database of luminescent Minerals


SCHEELITE


Chemical Formula: CaWO4

Familly: Tungstates, Molybdates

Status: IMA-GP

Crystal System: Tetragonal

Mineral for Display: Yes

Associated names (luminescent varieties, discredited names, synonymes etc.):  cuproscheelitemolybdoscheelite

Luminescence:


UV Type Main color Intensity Observation Frequency
Long Waves (365nm):      Violet Pink Very weak
Short Waves (254 nm):      Bluish White Very StrongAllways
Other colors LW:     
Violet red ,
Other colors SW:     
White ,

Daylight Picture


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

Short Waves Pictures (254nm)


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

 

Galerie de photos:

            ...

     To the gallery (8 images in the gallery)


Phosphorescence (in the common meaning of the term) seen by naked eye:


No Data

Thermoluminescence: Yes


Comments:


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


Main Activator(s) and spectrum:


Most Common Activator: WO42-

Other activators:            Sm3+ , Eu3+ , Dy3+ , Tb3+ , Pr3+ , Nd3+ ,

Peaks in the spectrum (nm):

WO42-: Broad band centered at 425 - 435nm
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.

            ...

  To the spectrum gallery (9 spectra in the gallery)


Comments on activators and spectra:


Broad band centered at 425 - 435 nm activator: (WO4)2- ;
Peaks in relation with the presence of REE: 488 et 575 (Dy3+), 609 et 647 (Sm3+), 439 (Tb3+) et 607 (Pr3+); the pegmatitic and hydrothermel scheelite  shows the lines of Erbium and Terbium, while scheelite occurences related to eruptive complexe and sulfide ore shows dominantly the lines of the REE of the Cerium group.
Green emission due to (MoO4)2-(Tarashchan) or possibly Pb (Blasse).
The natural photoluminescence emission of ordered CaWO4 is attributed to an intrinsic slight distortion of the [WO4] tetrahedral.
Lifetime: 9μs (@ 405nm);

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 Locality for luminescence(*):


(*)Data are not exhaustive and are limited to the most important localities for fluorescence


Bibliographical Reference for luminescence:



Luminescence Reference on internet:



Mineralogical Reference on internet:


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

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

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