Record details

Title
    Defect structure and luminiscence behaviour of agate : Results of electron paramagnetic resonance (EPR) and catodoluminiscence (CL) studies
Statement of responsibility
    J. Götze, M. Plötze, H. Fuchs, D. Habermann
Other titles
    Luminiscence Phenomena in Minerals: Thematic Set (Variant.)
Author
    Fuchs, H.
    Götze, J.
    Habermann, D.
    Plötze, M.
Language
    anglicky
Source title - serial
    Mineralogical magazine
Vol./nr.
    Vol. 63, no. 2
Pages
    p. 149-163
Year
    1999
Notes
    8 obr., 2 tab., 4 pl.
    plates po s.188
    Zkr. název ser.: Mineral. Mag.
Subject group
    achát
    defekt krystalu
    elektronová paramagnetická resonance
    katodoluminiscence
    krystalová struktura
    křemen
    prvky stopové
Geographical name
    Brazílie
    ČR-Čechy
    Frýdštejn (Jablonec nad Nisou)
    Kanada
    Kyje (Jičín)
    Mexiko
    Namibie
    Nová Paka (Jičín)
    SRN
    Velká Británie-Scotland
Keyword
    Agate
    Behaviour
    Catodoluminiscence
    CL
    Defect
    Electron
    EPR
    Luminiscence
    Paramagnetic
    Resonance
    Results
    Structure
    Studies
Abstract (in english)
   Samples of agate and quartz incrustations from different parent volcanic rocks of certain worl-wide localities were investigated by EPR, CL and trace element analysis. In all agate samples the following paramagnetic centres were detected: O23-, E'1, [AlO4], [FeO4/M+]O, and [GeO4/M]O. Centres of the type [TiO4/Li+]O and [TiO4/H+]O, which were detected in quartz of the parent volcanics, are absent in agate. Generally, the abundance of O23- centres (silicon vacancy) and E'1 centres (oxygen vacancy) in agate is remarkably higher than in quartz. The highdefect density in agates points to rapid growth of silica from strongly supersaturated solution probably with a noncrystalline precursor. CL microscopy reveals internal structures and zoning in agates and quartz incrustations which clearly differ from those discernible by conventional polarizing microscopy. The CL spectra of agates differ from those of quartz from crystalline rocks.
   At least three broad emission bands were detected in the CL spectra: a blue band of low intensity, a yellow band at about 580 nm, and an intense red band at 650 nm. The CL emission at 650 nm shows some relations to the hydroxyl or alkali content and theabundance of O23- centres and E'1 centres. The emission intensity increases during electron bombardement due to the conversion of different precursors (e.g. =Si-O-H, = Si-O-Na groups) into hole centres. Another conspicuous feature in the CL spectra of agates is the existence of a yellow emission band centred at around 580 nm. The predominance of the yellow CL emission band and the high concentration of E'1 centres are typical for agates of acidic volcanics and are indicative of a close relationship between the two
Contributor
    Česká geologická služba
Contributor code
    ČGS (UNM)
Source format
    U
Entered date
    19. 2. 2008
Import date
    8. 8. 2012