Secondary mineral developments and changing of fabric features due to chemical weathering and hydrothermal alteration are investigated in detail from a set of samples which were collected from weathering profiles developed on Harsit granitic rocks, NE Turkey. With the increasing degree of chemical weathering, the amount of unaltered mineral and micro petrographical indexes decrease and the amount of micro fissures and voids increase. The most resistance mineral for the chemical alteration is quartz. It can even be found as a fragments in completely weathered rocks. Feldspars start to alter to serisite, epidote and beidellite in hydrothermal stage and, disintegrates, non-stoichiometrically dissolve and decompose to clay minerals during weathering. Vermiculite, chlorite, epidote and Fe-Ti oxides are hydrothermal stage products of biotite and amphiboles and these alteration products are not stable under surface weathering and decompose to clay and ironeous compounds.