Database of luminescent Minerals


Chemical Formula: Ca3Al2(SiO4)3

Familly: Silicates

Status: IMA-GP

Crystal System: Isometric

Mineral for Display: No

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


UV Type Main color Intensity Observation Frequency
Long Waves (365nm):      Red Weak
Mid waves (320 nm):      Red Weak
Short Waves (254 nm):      Red Extremely weak
Other colors LW:                    
Bluish White , Violet red , Pink , Salmon pink ,
Other colors MW:          
Bluish White , Violet red ,
Other colors SW:               
Yellowish White , Orange , Dark Orange /Tawn ,

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:

No phosphorescence seen by naked eye whatever the type of UV

Thermoluminescence: Yes


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)

Col. G.Barmarin; Photo: G. Barmarin


  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(*):

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

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