Lijst van fluorescerende mineralen

CHRYSOBERYL

Scheikundige formule: BeAl₂O₄

Familie: Oxiden en Hydroxiden

Status: IMA-GP

Kristal Systeem: Orthorhombisch

Mineraal om tentoon te stellen: Nee

Fluorescentie:

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

Commentaar:

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

Activator en spectrum:

Voornaamste Activator: Cr³⁺

Andere activatoren: V²⁺ ,

Pieks in het 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)

Commentaar over activators en 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 R_1m (m for mirror, the first position for Al³⁺ replacement) and R_2m 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 R_1i (i for inversion) and R_2i 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;

Beste vindplaats voor fluorescentie(*):

• Takovaja River, Ural Mountains, Russia (var. Alexandrite fluo red);
• Izumrudnye Kopi area, Malyshevo, Sverdlovsk Oblast, Ural, Russia;
• Santa Teresa, Espirito Santo, Brazil (yellow SW);
• Haddam, Connecticut, USA (SW yellow green);

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

Referentie voor fluorescentie:

• 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 ,
• Luminescent Spectra of Minerals, Boris S. Gorobets and Alexandre A. Rogojine, Moscow, 2002 ,
• Handbook of Fluorescent Gems and Minerals, a practical guide for the gem and mineral collector, Jack de Ment, 1949 ,

Mineralogische Referentie op het internet:

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

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

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