Lijst van fluorescerende mineralen


SCHEELITE


Scheikundige formule: CaWO4

Familie: Tungstaten, Molybdaten

Status: IMA-GP

Kristal Systeem: Tetragonaal

Mineraal om tentoon te stellen: Ja

Fluorescerende variëteiten:  cuproscheelitemolybdoscheelite

Fluorescentie:


UV Type Kleur Intensiteit Frequentie van de observatie
Lange Golven (365nm):      Violet roos Zeer zwak
Midden Golven (320 nm):      Rood Middelmatig
Korte Golven(254 nm):      Blauw wit Zeer sterkAltijd
    
Andere kleuren lange golven:                    
Witte , Oranje geel , Oranje , Violet rood ,
Andere kleuren Midden golven:               
Oranje rood (Zalmkleurig) , Rood , Violet rood ,
Andere kleuren korte golven:                              
Witte , Gelig wit , Roos wit , Bleek geel , Bruin , Geelachtig ,

Daglicht foto


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

Korte golf foto (254nm)


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

 

Foto galerij:

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     Naar de volledige galerij (8 beelden in totaal)


Fosforescentie (in de algemene betekenis) zien met het blote oog:


No Data

Thermoluminescencie: Ja


Commentaar:


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 en spectrum:


Voornaamste Activator: WO42-

Andere activatoren: Sm3+ , Eu3+ , Dy3+ , Ho3+ , Er3+ , Tb3+ , Pr3+ , Nd3+ , Yb3+ , Tm3+ ,

Pieks in het spectrum (nm):

WO42-: 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.

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  Vers la galerie de spectres (9 spectres au total)


Commentaar over activators en spectra:


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.

 


Beste vindplaats voor fluorescentie(*):


(*)Gegevens zijn niet exhaustieve, ze zijn beperkt tot de meest belangrijke plaatsen voor fluorescentie


Referentie voor fluorescentie:



Referentie voor luminenscentie op het internet:



Mineralogische Referentie op het internet:


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

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

Onderzoek op Internet:

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  Onderzoek op Wikipédia


 

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Snel opzoeking van een fluorescerend mineraal: