Knowledge of the relative complex permittivity is required to determine the differential absorption of microwave energy in an aggregate of minerals (rock). Electrical properties are also essential in modeling electromagnetic wave propagation and interaction in layered earth models (gas and oil exploration), remote sensing of ore deposits, and detection of pollutants in groundwater. In this U.S. Bureau of Mines research measurements at 24 deg c at frequencies from 1 to 22 ghz of the complex relative permittivities of dry pulverized samples of 10 minerals, 6 silicates and 4 metal oxides, showed that the permittivities of 1 mineral from each class, pyroxene (salite) and goethite, were practically independent of frequency. The other metal oxides, hematite, ilmenite, and manganese oxide (hollandite), had high permittivities that decreased significantly with increasing frequency. The dielectric loss factor of manganese oxide (hollandite) revealed a dielectric relaxation in the 1- to 22-ghz range with losses peaking between 2.45 and 11.7 Ghz. The other silicates, amphibole (richterite), chlorite (clinochlore), feldspar (labradorite), and muscovite and phlogopite micas, had lower permittivities that showed moderate reductions with increasing frequency. Their loss factors showed relatively little frequency dependence, but moderate reductions with increasing frequency were evident for amphibole (richterite), feldspar (labradorite), and pyroxene (salite).
Geophysics, V. 54, No. 10, Oct. 1989, PP. 1344-1349