Field distributions in samples composed of spherical, perfectly diamag
netic grains, randomly dispersed in a nonmagnetic matrix, are discusse
d on the basis of numerical calculations. Results of a spherical sampl
e of 580 identical grains, which occupy 58% of the volume, show that (
a) the dipole moment of the sample is in good agreement with effective
-medium theory predictions, (b) the superconducting volume fraction ca
n be infered from its measured dipole moment, and (c) the dipole part
of the actual field, to which a grain in this spherical sample is expo
sed varies from 70% of the applied field (near the poles) to 130% (nea
r the equator).