Mechanical drilling of boreholes on granite quarries of the Karelian Isthmus in view of high strength and abrasiveness of rocks - expensive and insufficiently productive method. For definition of possibility of application on granite quarries of fire drilling of boreholes by chair of open and drilling and blasting works of the Leningrad mining institute the drillability of granites of some deposits of the Leningrad area (Rovnoe, Erkil, Vozrozhdeniya and Kamennogorsky) is investigated. The studies were carried out with the use of small-scale jet burners (RGR-2, RTB-V5, MIRGEM), operating on oxygen-kerosene and benzene-air mixtures. Their technical characteristics are as follows ...