<p>This study focuses on the 3D characterization by X-ray CT of fractures induced by a roller crusher in silicate and calcite gangue minerals within rare earth element (REE)-bearing ore particles from the Mountain Pass mine, in order to evaluate CO₂ transport through the fracture networks. One hundred particles, crushed to a size of 4–7&#xa0;mm, were analyzed using X-ray radiography to distinguish between high-density gangue minerals (barite, bastnäsite, monazite) and low-density gangue minerals (silicates and carbonates). In this study, we focused on the low-density gangue minerals. Minerals such as calcite, present in the low-density phase, can react with CO₂, which is relevant for evaluating their interaction with the fracture networks. Based on the 2D cross-sectional views from X-ray computed tomography (XCT) and the mineralogical identification provided by TIMA (Tescan Integrated Mineral Analyzer), the analyzed low-density particles were classified into three categories: (i) mixed aggregates, (ii) particles composed mainly of calcite and silicates, and (iii) particles primarily composed of silicates. This classification was used to investigate how fracture patterns vary with mineralogical composition. Crack analysis using a voxel size of about 3–4&#xa0;µm revealed distinct fracture patterns among these three classes. Random fracturing was observed in the mixed aggregates, while preferential boundary cracks were found in the calcite and silicates separated particles. Large cracks were observed in separated silicates. To assess the role of the cracks in CO₂ transport, the Lattice Boltzmann Method (LBM) was used to simulate permeability and fluid flow velocity. The results indicate that the fractures can serve as pathways for CO₂ mobilization to calcite. These findings contribute to a broader project assessing the feasibility of CO₂ storage.</p>