Influence of Mineral Composition and Microstructural Features on the Tensile Failure Mechanisms of Granite and Marble

A comprehensive mineralogical analysis of granite and marble rocks was conducted using powder X-Ray Diffraction (XRD) and Scanning Electron Microscopy coupled with Energy-Dispersive Spectroscopy (SEM-EDS). The comparative evaluation of XRD and SEM-EDS data revealed a strong correlation, confirming the congruence of mineral compositions derived from both techniques. Detailed oxide composition analyses of Aswan red, light grey, and dark grey granite samples indicated a high degree of similarity, with trace elements such as C, O, Na, Al, K, and Ca uniformly dispersed within the silica matrix. The granite specimens were classified as peraluminous, predominantly composed of quartz, feldspar, and iron-aluminum oxides. In contrast, white marble samples, largely comprising carbonate minerals, exhibited distinct mineralogical characteristics. Mechanical testing using the Brazilian disc method has demonstrated that mineral composition significantly influences tensile strength. Because of its high SiO2 content and interconnecting crystalline structure, light grey granite has the maximum tensile strength, 1.45 MPa. Aswan red and dark grey granites showed similar mechanical reactions, according to their similar mineralogy, with tensile strengths of 1.42 MPa and 1.37 MPa, respectively. The composition of white marble, which contains dolomite and calcite, which are naturally less resistant to tensile failure, resulted in the lowest tensile strength of 0.89 MPa. The results confirm that feldspar and SiO2 minerals are essential for improving the mechanical integrity of granite. Conversely, the lower tensile strength of white marble is consistent with a softer mineralogical structure. Major Findings: Light grey granite has higher tensile strength than aswan red and dark grey granites because of high SiO2 content. White marble has the lowest tensile strength because of high calcium and magnesium content and soft mineralogical structure. Tensile strength data from the Brazilian disc method provides the insight of impact of mineral composition on mechanical properties.