Both porosity and water content of rocks, sediments, and soils can be estimated from measurements of the effective dielectric permittivity. To achieve accurate modeling to obtain either water content or porosity the permittivity of the solid phase must be known. Until recently the most common method of obtaining the permittivity of the solid phase of granular materials relied on packing samples in air and using a mixing model to estimate the permittivity of the solid. This approach preassumes the correctness of the mixing models that we want to test. This work develops a recently proposed immersion methodology suitable for fine-grained mineral samples and clay minerals. Measured permittivity values were 4.4 for ground quartz, 9.1 for Iceland Spar calcite, 6.0 for biotite mica, 5.8 for phlogopite mica, 5.3 for talc, 5.1 for kaolin, 5.8 for illite, and 5.5 for montmorillonite. The methodology was found to work well other than for the high surface montmorillonite sample where the immersion polar fluid adsorbed to the clay.