Postgenetic alteration processes (e.g. hydrothermal alterations), accompanied by brittle failure and secondary mineral fillings, are a common phenomenon in granites used as a building block. Alterations are manifested by discrete phenomena in rock-forming minerals and internal structure (transformation of more basic nuclei of plagioclase, recrystallization of quartz aggregates and formation of discrete microcracks, filled with clay minerals). The issue of the influence of these discrete mineralogical and microstructural transformations on mechanical properties and on the response to weathering processes has so far escaped the attention of research. One of the reasons may be the fact that these discrete changes in the original igneous rock structure affect only minimally on the tested strength characteristics, but they significantly affect the deformation properties and energy characteristics of the deformation process. Similarly, the influence of the type of mineralization in microcracks and the degree of saturation on the deformation behavior and on the susceptibility to failure by weathering processes is not investigated.