A cartridge for breaking rock which includes a tubular housing in which is formed a first compartment. The cartridge includes a first energetic composition inside the first compartment and a primer which is exposed to the first energetic composition. The cartridge includes a second compartment inside the tubular component and a plunger inside the tubular component which is movable under explosive force towards the primer. The cartridge still further includes a second energetic composition inside the second compartment and an actuator and a fuse for initiating the second energetic composition. The actuator has an area which is smaller than the cross-sectional area of the plunger and is movable, by movement of the plunger, towards the primer, and in that the primer is initiated by the actuator only when liquid fills a volume enclosed at least partly by surfaces of the actuator and of the primer.