It is well known that the rock mass mechanical properties, both in terms of deformability and strength, are deeply influenced by the presence of discontinuities. Their characterization is of paramount importance in any engineering design of rock related projects. This thesis presents an experimental campaign aimed at investigating the geometrical and mechanical characteristics of fracture surfaces obtained by tensile splitting. Four different rocks have been considered: Balma Syenite, Absolute Black Gabbro, Pink Porriño Granite and Carrara marble. Prismatic samples have been tested for determining the deformability properties, by means of unconfined compression tests. Then, for each sample a tensile fracture has been induced by means of Brasilian-like tests.