<p>The shape characteristics of mineral crystal particles dictate their mechanical behavior and fracture patterns. This study systematically classifies mineral crystal particle shape characteristics in rocks, focusing on roundness, aspect ratio, and non-circular particle proportion. Using theoretical, numerical, and experimental methods, it reveals how these characteristics influence rock mechanical properties. As particle roundness decreases or the proportion of non-circular particles increases, contact points and eccentric moments between particles rise, reducing rolling capacity. This results in higher uniaxial compressive strengths (UCSs), elastic modulus (E), and crack initiation strains, along with increased accumulated friction energy. As the aspect ratio of mineral crystal particles increases, their rolling capacity decreases due to higher eccentric moments, while sliding capacity increases due to greater contact distances. When the aspect ratio deviates from 1.2:1 to 1.4:1, UCSs, E, and crack initiation strains rise, and accumulated friction energy increases. The final main fracture surface of the rocks becomes more parallel to the loading axis. As the roundness of mineral crystal particles increases, or as the aspect ratio of these particles deviates from 1.25:1, the mode of rock failure shifts from shear fracture to tensile fracture. Additionally, the final damage zone of the rocks becomes more fragmented with an increase in the proportion of non-circular mineral crystal particles. These findings lay the groundwork for understanding how microstructure influences the macroscopic mechanical behavior of rocks, thereby revealing rock fragmentation mechanisms that can optimize mining design and support parameters.</p>