This study is focus on the petrographic properties and geo-mechanical properties of the Inzari formation rocks at Tar Khel Village, District Swabi, Khyber Pakhtunkhwa, and whether they are suitable for use as building materials for structures like bridges, buildings, and roads. Five fresh and large samples have been taken from various areas of this formation. These rock samples were identified as siliciclastic mudstone through a careful petrographic analysis. The test result of physical properties (water absorption, specific gravity, and porosity) and mechanical properties (unconfined compression strength, unconfined tensile strength, Schmidt hammer test, and shear strength) of these rock samples shows as follows: their unconfined compressive strength with between 23 to 94 MPa, their specific gravity values being very high (≥2.78), and their porosity and water absorption values being very low (<1%), imply that the Inzari formation rock can be used as an excellent building material. The rock sample strength variations may be mainly caused by the presence and abundance of stylolite and fractures. Furthermore, the petrographic property analysis of these rock samples indicates that they have the significant amount of micrite and calcite, which are suitable to be use as both asphalt and concrete aggregate. According to this study, the Inzari formation rock is appropriate for use as fine aggregate in concrete, asphalt, and other building materials.