Fig. 5. Effective permittivity of coarse-grained (500 µm) natural calcite sample (Iceland Spar) obtained from a single calcite crystal that was crushed. The calcite powder was a synthetically made sample that was very fine-grained (0.1 µm). The solid symbols represent the estimated permittivity with 95% confidence estimates, Iceland Spar _s = 9.1; Micro-crystalline calcite _s = 8.3. The forth point for the micro-crystalline calcite lies directly under the estimate, giving perhaps greater confidence in the value of 8.3 than the confidence estimate might suggest.