—We present results of experimental measurements of complex dielectric permittivity (CDP) of sand and powders of quartz granules with mass-averaged particle sizes from 5 to 250 μm, saturated with distilled water and NaCl solutions with a conductivity of up to 0.77 S/m. The CDP spectra are measured in a frequency range from 1 kHz to 8.5 GHz. Spectra at frequencies above 1 GHz are simulated using a refractive three-component mixture model. The CDP spectra in a frequency range from 10 kHz to 1 GHz were simulated by three relaxation processes using the Debye and Cole–Cole equations. It is shown that the conductivity of the sample at a frequency of ~5 kHz is not proportional to the conductivity of the saturating solution. The strengths of the two low-frequency processes are more closely correlated with the sample conductivity than with the solution proportion. The relaxation times of the low- and high-frequency processes are statistically related to an average particle size, and the relaxation time of the low-frequency process is additionally correlated with the specific surface area of the particles. We estimated the conductivity of the saturating solution at which the correlation is the strongest.