Geologic and Geotechnical Investigation of Basement Rocks and Mesozoic Sandstone for Dimension Stone Potential in Northwestern Ethiopia

Abstract This study evaluates the suitability of various rock types for dimension stone applications through a combination of fieldwork, petrographic analysis, and geotechnical testing. The rocks investigated include Mesozoic sandstone, Precambrian migmatite gneiss, syn-tectonic granite, syn-to late-tectonic gabbroic diorite, and late to post-tectonic granite. Extensive field observations documented these rock unit’s spatial distribution, weathering patterns, color, texture, and deformation features. Petrographic analysis focused on mineralogical composition, alteration and texture while geotechnical tests assessed uniaxial compressive strength (UCS), density, water absorption, and porosity. The findings reveal that mineral composition significantly affects rock strength: quartz and feldspar rich rocks exhibited higher UCS, whereas rocks containing weaker minerals like biotite and muscovite showed lower strength. All tested rocks except Mesozoic sandstone, demonstrated low porosity, low water absorption, and high UCS, can make them ideal for both structural and decorative dimension stone applications. Mesozoic sandstones with its higher porosity and lower UCS, is more appropriate for non-structural decorative use. This study underscores the importance of integrating fieldwork with petrographic and geotechnical tests when evaluating rocks for dimension stone applications. The result highlights the need for careful rock selection based on the petrographic properties, visual appearance, alteration degrees, and physico-mechanical characteristics to optimize stone use in construction and decorative projects. Future research should focus on the performance of these rocks under harsh environmental conditions to ensure long term durability.