This book represents a comprehensive geo-mechanical study of the magmatic rocks represented by a wide range of varieties; it is structured into three parts, experimental and interpretation of experimental data, showing the methodology to assess the quality of igneous rocks analyzed, and the results of theoretical and experimental research carried out on the analyzed rock types. A new ranking method is proposed, based on considering the rock characteristics as indicators of quantitative assessment, and the grading system, by given points, allowing the rocks framing in admissibility classes. Applying this evaluation system allows determining the specific parameters of the rock quality requirements, namely the conformity and unconformity degrees, and more specifically the safety level that these rocks can provide if they are used in the construction field, either as aggregates or as construction materials. The proposed method represents an appropriate tool for assessment and verification of the requirements regarding the quality of rocks used in construction. The last part includes a general classification of analyzed magmatic rocks based on the geomechanical assessment model.