I make use of the following marbles; Carrara, Espirito Santo, Giallo Siena, etc, the granites are; Ouro-Velho( old gold ), Juparana, etc, and the quartzite are; Onyx, Azul Macaúbas,etc. The hardness of the stones is measured by the Mohs scale, that ranges from 1 to 10 in this order; 1( softest ) = talc, and 10( hardest ) diamond.Marbles are classified with 3 points, granites with 5 points and quartzite with 7 points. Three kinds of tools are needed to work with these stones.Manual tools: mallet, pointer,files,etcElectrical tools: chisel, drills etc. Pneumatic tools: pneumatic drills, pointers, chisels, etc.