1. Intact rock contains neither joints nor hair cracks.
Hence, if it breaks, it breaks across sound rock. On account of
the injury to the rock due to blasting, spalls may drop off the
roof several hours or days after blasting. This is known as a
spalling condition.
Hard, intact rock may also be encountered in the
popping condition involving the spontaneous and violent
detachment of rock slabs from the sides or roof.