Phys Chem Minerals (1992) 19:157-165

Dielectric Constants of Apatite, Epidote, Vesuvianite, and Zoisite, and the Oxide Additivity Rule

Robert D. Shannon

Central Research and Development, Experimental Station 356/329
E.I. Du Pont de Nemours, Wilmington, DE 19880-0356, USA

George R. Rossman

Division of Geological and Planetary Sciences, California Institute of Technology
Pasadena, CA 91125, USA


The dielectric constants and dielectric loss values of 4 Ca-containing minerals were determined at 1 MHz using a two-terminal method and empirically determined edge corrections. The results are:

vesuvianite l   9.93 tand 0.006
    9.79   0.005
vesuvianite 2   10.02   0.002
    9.85   0.003
zoisite l   10.49   0.0006
    15.31   0.0008
    9.51   0.0008
zoisite 2 K a 10.55   0.0011
  K'b 15.45   0.0013
  K c 9.39   0.0008
epidote K'11 9.52   0.0008
  k'22 17.1   0.0009
  k'33 9.37   0.0006
fluorapatitel K a 10.48   0.0008
  K c 8.72   0.0114
fluorapatite2 K a 10.40   0.0010
  K c 8.26   0.0178

The deviation (A) between measured dielectric polariza bilities as determined from the Clausius-Mosotti equa tion and those calculated from the sum of oxide polarizabilities according to aD (mineral) = S aD (oxides) for ve suvianite is ~0.5%. The large deviations of epidote and zoisite from the additivity rule with A= + 10.1 and + 11.7%, respectively, are attributed to "rattling" Ca ions. The combined effects of both a large F thermal parameter and possible F-ion conductivity in fluorapatite are believed to be responsible for A = + 2-3%. Al though variation of oxygen polarizability with oxygen molar volume (V0) is believed to affect the total polarizabilities, the variation of V0 in these Ca minerals is too small to observe the effect.