Database of luminescent Minerals


Chemical Formula: BeAl2O4

Familly: Oxides and hydroxides

Status: IMA-GP

Crystal System: Orthorhombic

Mineral for Display: No

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


UV Type Main color Intensity Observation Frequency
Long Waves (365nm):      Red Very weak
Mid waves (320 nm):      Red
Short Waves (254 nm):      Red Very weak
Other colors SW:     
Greenish Yellow ,

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

No phosphorescence seen by naked eye whatever the type of UV


Varété alexandrite: fluorescence rouge due au chrome (Cr2+)
Chrysobéryl classique: jaune vert, crème, verdâtre;

Main Activator(s) and spectrum:

Most Common Activator: Cr3+

Other activators:            V2+ ,

Peaks in the spectrum (nm):

Cr3+ replacing Al  : 678, 680 nm 

V2+ : band around 720 nm (80nm half-width)  (Gaft), 

VO6 : broad band at 645nm (FWHM: 120nm)

TiO6 : 516nm (FWHM: 115nm) (Gaft), band at 540 nm (Gorobets), 

689, 698, 703nm (Gaft)

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

Comments on activators and spectra:

The Al3+ ions are octahedrally coordinated by the oxygen ions and occur in two not equivalent crystal field sites in the lattice.

The Cr3+ ions replace substitutionally the Al3+ ions, 78 % replacing Al3+ ions in one position and the rest going into the second sites.

The major features of the spectra at 300 K are the two sharp lines R1m (m for mirror, the first position for Al3+ replacement) and R2m peaking at 680 nm and a broad, structured band peaking at lower energies. The 689.5 and 695.2 nm decay time is much larger than that for the 677.9 and 679.5 nm emission (Suchoki et al. 1987).

At certain excitation wavelengths, such as 488nm, the R1i (i for inversion) and R2i peaking at 690.0 and 695.0 nm lines associated with Cri ions in inversion sites (second site) appear (Powell et al. 1985)


The Cr3+ luminescence properties in natural chrysoberyl minerals have been studied as a function of the Cr content as well as impurities such as Fe and V.

A competition was found between Cr and V for very low Cr concentration with the vanishing of Cr3+ emission from Cr3+ ions located in inversion site. The Fe3+ ions

substitute in mirror site efficiently with a strong impact on the Cr3+ lifetime of mirror site (Ollier et al. 2015).


Cathodoluminescence: red;

Best Locality for luminescence(*):

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

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