Database of luminescent Minerals

GROSSULAR

Chemical Formula: Ca₃Al₂(SiO₄)₃

Familly: Silicates

Status: IMA-GP

Crystal System: Isometric

Mineral for Display: No

Luminescence:

Daylight Picture

GROSSULAIRE Lake Jaco, Chihuahua Mexico;
Col. G.Barmarin; Photo: G. Barmarin

Long Waves Picture (365nm)

GROSSULAIRE Lake Jaco, Chihuahua Mexico;   UVLW
Col. G.Barmarin; Photo: G. Barmarin

Short Waves Pictures (254nm)

GROSSULAIRE Lake Jaco, Chihuahua Mexico;   UVSW
Col. G.Barmarin; Photo: G. Barmarin

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

Thermoluminescence: Yes

Comments:

Grossular garnet from Lake Jaco, Chihuahua Mexico, may be found as dark cherry red crystals, with vesuvianite.

Under either MW or a filtered high pressure UV source, these garnets fluoresce brilliantly in a pure red.

Mont-Saint-Hilaire: grossular OH-bearing (hibschite)

Main Activator(s) and spectrum:

Most Common Activator: Cr³⁺

Other activators:            Mn⁴⁺ , Mn²⁺ , V²⁺ ,

Peaks in the spectrum (nm):

Broad band peaking at 611nm, peak at 489nm and 713nm (échantillon en collection)

Cr³⁺ : Lines at 690, 694, 698 and 707nm

Mn²⁺ substituting to Ca²⁺ : band around 590 -605 nm

Mn³⁺ : broad band at 653nm

Mn⁴⁺ : broad band at 670nm

V²⁺ : peak at 717 nm  (Gaft)

  To the spectrum gallery (1 spectra in the gallery)

Comments on activators and spectra:

The color is identical to that of red-fluorescing ruby corundum or spinel. As with those minerals, chromium in place of aluminum is the likely activator. Other activator: V²⁺ (717 nm), Nd³⁺ (462, 476, 482,501 nm) and possibly Mn²⁺ band around 605-610 nm (decay time: several ms).

Natural grossular luminescence was studied by continuous wave (CW) luminescence technique and has been connected with Cr³⁺ centers, which substitutes for Al³⁺ and occupies a site with distorted octahedral symmetry (which in fact is trigonal C3i). Trivalent chromium in grossular occupies high crystal field position.

The luminescence spectra of Cr3+ in grossular at room temperature contain a strong broad band peaking at 720 nm and three sharp lines centered at 697, 700 and 701 nm.

Excitation by CW laser with 785 nm revealed IR luminescence lines which evidently may be ascribed to trivalent REE, such as Pr, Ho, Nd, Er and Yb (Gaft).

Best Locality for luminescence(*):

• Lake Jaco, Chihuahua Mexico;
• Jeffrey Mine, Asbestos, Les Sources RCM, Estrie, Québec, Canada (pink under LW);
• Lelatema Mountains, near Arusha, Tanzania (colorless crystal luminescent in strong apricot color under SW);
• variety hessonite from Beaver Mine, Thetford Mine, Quebec, Canada (bright orange under SW);
• King mine, Thetford Mines, Les Appalaches RCM, Chaudière-Appalaches, Québec, Canada (orange SW);
• Sierra de Cruces, Mun. de Sierra Mojada, Coahuila, Mexico;

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

Bibliographical 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 ,
• Luminescence Spectroscopy of Minerals and Materials, M. Gaft, R. Reisfeld, G. Panczer, Springer Editor, ISBN: 10 3-540-21918-8 ,

Luminescence Reference on internet:

• MONT-SAINT-HILAIRE, History, Geology, Mineralogy, Laszlo HORVATH, The Canadian Mineralogist, Special Publication 14, 2019




Images:

 

• Jeffrey Mine, Asbestos, Québec, Canada: http://www.mindat.org/photo-698392.html
• King mine, Québec, Canada: http://www.mindat.org/photo-240464.html

Mineralogical Reference on internet:

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

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

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