Mechanical drilling of boreholes in granite quarries of the Karelian Isthmus due to high strength and abrasiveness of rocks is an expensive and insufficiently productive method. To determine the possibility of application at granite quarries of fire drilling of boreholes by the department of open pit and drilling and blasting works of the Leningrad Mining Institute, the drillability of granites of several deposits of the Leningrad area (Rovnoe, Erkil, Vozrozhdeniya and Kamennogorsky) was investigated. The studies were carried out with the use of small-scale jet burners (RGR-2, RTB-V5, MIRGEM), operating on oxygen-kerosene and benzine-air mixtures. Their technical characteristics are as follows ...