Tuff (from the
Italian tufo) is a type of
rock made of
volcanic ash ejected from a
vent during a
volcanic eruption. Following ejection and deposition, the ash is compacted into a solid rock in a process called
consolidation. Tuff is sometimes called
tufa, particularly when used as construction material, although
tufa also refers to a quite different rock. Rock that contains greater than 50% tuff is considered tuffaceous.