The bombs are pieces of magma hurled from the crater still in the fluid state. The term lapilli is often used instead of pumice or scoria, which possess a vesicular structure. The difference between scoria and pumices is given by the different chemical composition, instead of the size. The pumices have a light colour, whereas scoriae have generally a black or reddish-black colour. The pyroclastic products emitted by a volcano during explosive eruptions form, upon aggregation and consolidation, pyroclastic rocks.
Pyroclastic breccia is a rock made up mostly by blocks and bombs.
Lapillistone is a rock mostly made of lapilli. The joints have a direction perpendicular to the flow. Degassing structures, called pipes , are often observed in pyroclastic-flow deposits emplaced at high temperature. These structures consist of a vertical alignment of coarse material without fine particles, because they were extracted by hot gases escaping from the deposit.