<p>To investigate the influence of the mineral composition on the deformation and failure mechanism of heterogeneous rock bodies, this study determined the mechanical properties of mudstone through laboratory experiments, and then built a crystal model Particle Flow Code-Grain Boundary Model (PFC-GBM) based on particle flow. The stress-strain curve of mudstone was calibrated, and a custom program for monitoring the evolution of cracks within and between minerals during the rock failure process was developed using the Fish language. The deformation and failure mechanisms of mudstone were analyzed based on acoustic emission theory and crack distribution diagrams. The results reveal the following: (1) the anisotropy in the failure process of the heterogeneous crystal model of mudstone was confirmed, with the failure being predominantly characterized by linear shear damage. (2) Changes in the mineral composition affect the evolution of cracks at different stages of mudstone failure, and as the clay mineral composition increases, the damage caused by the relative movement between minerals is no longer the main form of failure. (3) Based on the failure results, an increase in the clay mineral composition corresponds to three distinct mudstone failure modes, each characterized by specific crack distribution patterns.</p>