Database of luminescent Minerals


BARYTE


Chemical Formula: BaSO4

Familly: Sulfates

Status: IMA-GP

Crystal System: Orthorhombic

Mineral for Display: Yes

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

Luminescence:


UV Type Main color Intensity Observation Frequency
Long Waves (365nm):      Yellowish White MediumOften
Mid waves (320 nm):      Yellowish White Medium
Short Waves (254 nm):      Yellowish White MediumRarely
Other colors LW:                              
Bluish White , Pale Yellow , Orangy yellow , Orange , Greenish white , Yellowish ,
Other colors MW:                              
Bluish White , Pale Yellow , Orangy yellow , Orange , Greenish white , Yellowish ,
Other colors SW:                                   
Bluish White , Pale Yellow , Orangy yellow , Orange , Salmon pink , Greenish white , Yellowish ,

Short Waves Pictures (254nm)


Baryte (fluo cream) in calcite (fluo red) SW,
Franklin Mine, Sussex Co., New Jersey, USA
Col. G. Barmarin; Photo: G. Barmarin

 

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


UV Type Color Intensity Observation Frequency
Long Wave (365nm): Yellowish White
Mid Waves (320 nm): Yellowish White
Short Waves (254 nm): Yellowish White
 

Comments:


Mineral barite is one of the first luminescent materials from which the famous Bologna stone was obtained.

Nevertheless, up today the understanding of natural barite luminescence is very scarce.

It has been known for a long time that some specimens of barite are fluorescent under UV exposure and emit white, yellow, green or orange light.

In steady-state luminescence spectra of barite different luminescence bands from the UV to the red part of the spectrum have been detected.

However, only UO22+ and Eu2+ luminescence centers have been confidently identified (Tarashchan 1978; Gaft et al. 1985).

Laser-induced time-resolved technique enables to detect Ag+, Bi2+, Bi3+, Eu2+, Eu3+, Ce3+, Nd3+, (UO2)2+ and several still not identified emission centers (Gaft et al. 2001, 2008b) 


Main Activator(s) and spectrum:


Most Common Activator: (UO2)2+ (Uranyl ion) as impurities

Other activators:            Pb2+ , S2- , Organic impurities , Cu+ , Eu2+ , Ce3+ , Tb3+ , Ag+ , Nd3+ , Bi2+ , Bi3+ ,

Peaks in the spectrum (nm):

Bi3+ : 426-430nm band 80nm half-width  ( τ = 750 microsecondes)

Bi2+ replacing Ba2+ : narrow band 625nm  ( τ = 5 microsecondes)

Ag: very broad band (150 nm half-width) peaking at 635nm  ( τ = 225 microsecondes)

Ce3+  : 302, 305, 330, 360nm 

Nd3+  : 389, 446, 589, 672nm  

Eu3+ : 592, 620, 701nm

Tb3+  : 488, 544nm  

UO22+  : 501, 522, 544, 568 

Eu2+  : 375, 613, 615, 697nm 

Pb      : blue part of the spectrum


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

            ...

  To the spectrum gallery (7 spectra in the gallery)


Comments on activators and spectra:


It is known that the luminescent centers Eu2+ (1.24–1.40 Å), Ce3+ (0.88–1.02 Å), Nd3+ (0.99–1.15 Å), Tb3+ (0.89–1.09 Å), Ag+ (1.13–1.26 Å), Sn2+ (0.93 Å) substitute for Ba2+ (1.35–1.44 Å) or Sr2+ (1.10–1.27 Å), which are in 12-fold coordination in the barite structure (all ionic radii are for the 6-coordination form) (GOROBETS, 2002; GAFT et al., 2005);

A possible accommodation for the established in this study Eu3+ (0.97–1.13 Å) is also isomorphic substitution for Ba2+ or Sr2+


Ag+ (large pic 635 nm), Bi2+ in Ba2+ site (narrow band 625 nm), Bi3+ (426 nm), Eu2+ (375), Ce3+ (302, 330, 360nm), Nd3+ (446, 589nm) (Gaft)

Activators: (UO2)2+

UO22+ can be determined from the vibrational structure and the long decay time of the luminescence band.

Two different types of uranyl could be detected in Baryte: thin films of uranyl mineral considered to be a result of chemical adsorption (GOROBETS, 2002) and a solid solution of uranyl ion in barite crystal.

Activators:  Eu2+

Eu2+ can be determined from the spectral position, the half-width and the characteristic decay time of the luminescence band.

 

Mn2+ and Ag+ can be determined by comparing luminescence bands spectral parameters to those of synthesized BaSO4−Mn and BaSO4−Ag.


Fe3+ or Mn4+ can be determined from the spectral-kinetic parameters of the luminescence bands.( After M. Gaft and I. Rudenkova, Laser-induced luminescence of barite after thermal treatment, Journal of Thermal Analysis and Calorimetry vol42, 1994)


In natural barite the narrow orange band with λmax=625 nm, Δ=40 nm and τ=5 μs is connected with Bi2+ center.
The narrow violet band with λmax=625 nm, Δ=35 nm and τ=1.7 ms is connected with Bi3+ center.
The broad red band with λmax=635 nm, Δ=140 nm and τ=270 μs is connected with Ag+ center. The emission bands of Ag+ result from d9s–d10 transitions
The broad red band with λmax=750 nm, Δ=110 nm and τ=350 μs is connected with Cu+ center.(The luminescence of Bi, Ag and Cu in natural and synthetic barite , M. Gaft, R. Reisfeldb, G. Panczer, G. Boulonc, T. Saraidarovb and S. Erlishd, Optical Materials, vol16, 2001)

The luminescence spectrum (excitation of 266 nm, without delay, broad gate of 9 ms) of the studied endogenous barite contains 2 relatively narrow ultraviolet bands: one peaking at 306 nm and the other at 375 nm. The first band has a very short decay time and disappears after D = 50–100 ns. Such a combination of spectrum and decay time parameters is evidence that the luminescence is connected with Ce3+. The emission of Ce3+ corresponds to transitions between 5d1 and 4f1 electronic configurations. The second band has a longer decay time of approximately 1 μs and belongs to Eu2+ (GAFT et al., 2005). The Emission spectra of Eu2+ result from electronic transitions between 4f7 and 4f65d1 electronic configurations. After a delay of several μs, the Eu2+ emission becomes much weaker and very weak narrow lines appear, peaking at 488, 544 and 615 nm ). These lines are connected with trivalent rare-earth elements, which are characterized by relatively long decay times of hundreds of μs: the first 2 lines certainly belong to Tb3+ and the last one is principally typical for Eu3+ (GAFT et al., 2005). While Eu2+ luminescence is common, Eu3+ emission is here detected for the first time in barite. Under the excitation of 532 nm, a luminescence line at 615 nm dominates the spectrum, accompanied by several lines near 700 nm. Such behavior confirms that Eu3+ is responsible for these luminescence lines. The emission of Eu3+ corresponds to f–f transitions – from the excited 5D0 level to the 7Fj (j=0, 1, 2, 3, 4, 5, 6) levels of the 4f6 configuration.
The different emission spectra at excitations at 266 and 532 nm suggest at least 2 structural positions for Eu3+ in the barite crystal lattice.

(Spectroscopic study of barite from the Kremikovtsi deposit (Bulgaria) with implication for its origin, MAYA DIMOVA, GERARD PANCZER & MICHAEL GAFT, ANNALES GÉOLOGIQUES DE LA PÉNINSULE BALKANIQUE, Vol67, 2006 See link below)


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=Baryte

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

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