Porphyry: name of an effusive and eruptive rock, acid, chymically correspondent to granites formed by quarts phenocrystals, ortoclasium and mica, anfibolo and piroxenum dipped in a compact quartzum feldspatic matrix with or without brown- reddish vitreous substance. Porphyry  is really hard, sawble with a really high imbibition coefficient.