Introduction: An earlier study of the lunar regolith [1] demonstrated that the lunar surface soil was an extremely good absorber of microwave energy. Since then, efforts have been made to understand the mechanism for that exceptional absorption. It was speculated that the presence of nanophase iron was the unique component causing this absorption, however, our recent measurements on lunar soil samples and simulants [2,3] suggested that this might not be the case. It is known that micrometeorite impacts caused shock melting of lunar regolith leading to vaporization and re-condensation. This process has produced pieces of broken lunar rock and glassy agglutinates whose particles show sharp, jagged edges. The objective of this study was to evaluate whether the presence of a significant number of sharp-edged particles in a lunar simulant will enhance the microwave absorption of a sample. It is known that sharp edges of a sample heated in a microwave oven will tend to focus the electromagnetic fields leading to enhanced local heating. If these tests prove positive, the procedure used to obtain these sharp edged particles can be applied to produce new lunar simulants needed for evaluating how to efficiently process the lunar regolith. Validating the importance of sharp-edged particles in enhancing microwave heating could also have important commercial applications. Microwave Measurements: We studied two types of lunar simulants, a highland Chenobi composition and a mare JSC-2A composition. For the highland composition, we compared a well-characterized Feldspar (Anorthosite) rich simulant with about 70% angular and very angular particles to the same sample material after being processed in a ball mill for 1 hour to significantly reduce the number of angular and very angular particles. The resultant materials were passed though 100 mesh and 200 mesh screens to obtain 74 μm to 149 μm particles for microwave testing. The mare compositions consisted of basalt rich simulant samples that were also prepared in the same manner. Microwave studies were carried out at frequencies near 2.45 GHz. The room temperature resonant frequency and quality factor of the rectangular cavity’s TE103 – TE104 modes measured with and without the sample inserted, were used to determine the permittivity and permeability from a cavity perturbation approach [4]. The sample densities were determined by weighing the sample holder with and without the sample inserted. The TE103 mode (frequency = 2.161 GHz) determined the permittivity and the TE104 mode (frequency = 2.444 GHz) determined the permeability. The measured values are shown in Table I for samples with sharper particle edges and in Table II for samples with rounder particle edges. In comparing the magnitudes of the complex permittivity, ′′ ε , for both the sharper and rounder particle samples, we find that the mare sample values are over 3 times larger than the highland values, which is consistent with the measured heating curves, see Fig. 1. Similarly for the complex permeability, ′′ μ , for both sharper and rounder particle samples, we find the mare sample values are ~ 2 to 4 times larger, again consistent with the heating curves, see Fig 2. We also directly heated the simulant samples using a TWT microwave amplifier and compared their heating properties. These measurements were performed in the same microwave cavity used for the permittivity and permeability measurements. To accomplish this heating study, we assembled a high power microwave