Rivers of lava flow out when Etna erupts, before solidifying and turning into a dark grey stone.
The very hard and resistant “pietra nigra” (black stone) is used as a building material for walls and agricultural terraces in the countryside. It is worked in various ways according to its use: it is cut into regular blocks to build buildings, or slabs to pave roads.
All fragments and powder left over are reused to colour plasters or mortar mixtures.
