Over the past decade, researchers have investigated rock strength reduction due to microwave irradiation for the potential application in the mining and minerals industries to provide more efficient mine-to-mill practices. Minerals react differently facing microwave energy. They can intensely absorb microwave energy and heat up or be transparent to the wave, leading to various thermal expansions and stresses throughout the rocks. The thermal stresses create micro-cracks, resulting in rock strength reduction. Due to the complex nature of the method, the interactions between the electromagnetic waves, thermal responses, and micro-cracks generation are not well understood. In this study, a fully coupled numerical model is developed and validated against an experimental benchmark conducted in the Geomechanics Laboratory of McGill University with less than 10% error. This model provides insight into heat and energy transfer characteristics during microwave irradiation to improve the energy efficiency of mechanical excavation in different rock types and patterns. For that purpose, the importance of temperature-dependent rock properties is investigated, and it is shown that employing constant material properties in high microwave energy dosages leads to unrealistic conclusions. Furthermore, the existence of microwave-absorbing minerals within the rock is introduced as a significant parameter influencing the efficiency of the microwave treatment method. The results show that microwave-absorbing minerals can create substantial heat concentration during the irradiation, which can increase the microwave treatment efficiency significantly.