Physics and Chemistry of Minerals

, Volume 3, Issue 2, pp 117–131 | Cite as

Color centers, associated rare-earth ions and the origin of coloration in natural fluorites

  • H. Bill
  • G. Calas


Natural colored fluorites were studied by means of optical absorption and electron paramagnetic resonance (EPR). Complex centers involving rare-earth ions and/or oxygen give rise to the various colors observed. These include yttrium-associated F centers (blue), coexisting yttrium and cerium-associated F centers (yellowish-green), the (YO2) center (rose) and the O 3 molecule ion (yellow). Divalent rare-earth ions also contribute to the colorations, as for instance Sm3+ (green fluorites), or they are at the origin of strong fluorescence observed (Eu2+). Strong irradiation of the crystals with ionizing radiation leads to coagulation of color centers, and to precipitation of metallic calcium colloids. There is probably no simple relation connecting the coloration and the growth process of the crystal. Thermal stability studies, however, have allowed to partially classify the colors as being of primary or secondary origin.


Thermal Stability Electron Paramagnetic Resonance Fluorite Yttrium Optical Absorption 
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Copyright information

© Springer-Verlag 1978

Authors and Affiliations

  • H. Bill
    • 1
  • G. Calas
    • 2
  1. 1.Départment de Chimie PhysiqueUniversité de GenèveGeneve 4Switzerland
  2. 2.Laboratoire de Minéralogie-Cristallographie, associé au C.N.R.S.Université Pierre et Marie CurieParis Cedex 05France

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