Database of luminescent minerals 

ORTHOCLASE

Chemical formula: KAlSi₃O₈

Family: Silicates

Status: IMA-GP

Crystal system : Monoclinic

Display mineral: NON

Associated names (luminescent varieties, discredited names, synonyms, etc.): delawarite,  lennilite,  pierre de lune (moonstone),  adulaire, 

Luminescence:

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Phosphorescence (in the common sense of the term) observable with the naked eye:

No data

Thermoluminescence: OUI

Comments:

Adularia: SW and LW: Pink, violet, red, greenish, whitish.
Moonstone : SW: orange, red; SW: blue .

Activator(s) and spectrum:

Activator(s): Fe³⁺,

Peaks in the spectrum (nm):

Fe³⁺ repl. Al³⁺ or Si⁴⁺ : band peaking at 700nm 

No spectrum yet

Comments on spectrum and activators:

Polarized optical absorption spectra and laser-excited luminescence spectra have been measured on single-crystal Fe-rich orthoclase. The absorption spectrum consists of a series of sharp, weak bands that can be assigned to spin-forbidden crystal-field transitions of Fe³⁺ substituted on the tetrahedral Al³⁺ site of the feldspar structure. A broad-band luminescence in the deep-red region is the Stokes-shifted ⁴T₁ -> ⁶T₁, transition of tetrahedral Fe³⁺ and confirms the assignments to the absorption spectrum. The temperature dependence of the luminescence intensity can be accounted for by a phonon-assisted nonradiative decay proces.
(Absorption and luminescence of Fe³⁺ in single-crystal orthoclase, William B. White 1986 - see link below)
Time-resolved luminescence spectra of natural and synthetic hydrous volcanic glasses with different colors and different Fe, Mn, and H₂O content were measured, and the implications for the glass structure are discussed. Three luminescence ranges are observed at about 380–460, 500–560, and 700–760 nm. The very short-living (lifetimes less than 40 ns) blue band (380–460 nm) is most probably due to the ⁴T₂(⁴D) →⁶A₁(⁶S) and ⁴A₁(⁴G) →⁶A₁(⁶S) ligand field transitions of Fe³⁺. The green luminescence (500–560 nm) arises from the Mn²⁺ transition ⁴T₁(⁴G) →⁶A₁(⁶S). It shows weak vibronic structure, short lifetimes less than 250 μs, and indicates that Mn²⁺ is tetrahedrally coordinated, occupying sites with similar distortions and ion–oxygen interactions in all samples studied. The red luminescence (700–760 nm) arising from the ⁴T₁(⁴G) →⁶A₁(⁶S) transition of Fe³⁺ has much longer lifetimes of the order of several ms, and indicates that ferric iron is also mainly tetrahedrally coordinated. Increasing the total water content of the glasses leads to quenching of the red luminescence and decrease of the distortions of the Fe³⁺ polyhedra.

Cathodoluminescence: faint red.

Best localities for fluorescence (*):

• Khibiny Massif, Kola Peninsula, Murmanskaja Oblast, Northern Region, Russia

(*)The data are not exhaustive and are limited to a few remarkable localities for fluorescence

Bibliographic reference for luminescence:

• The Henkel Glossary of Fluorescent Minerals, Dr. Gerhard Henkel, Published by the FMS, 1989 ,
• Luminescent Spectra of Minerals, Boris S. Gorobets and Alexandre A. Rogojine, Moscow, 2002 ,

Reference for luminescence on the Internet:

Mineralogical reference on the Internet:

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

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

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