Tuff (from the Italian tufo) is a type of rock consisting of consolidated volcanic ash ejected from vents during a volcanic eruption. 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.
Read more about Tuff: Volcanic Ash, Breccias, Igneous Rock, Welded Tuff, Rhyolite Tuff, Trachyte Tuff, Andesitic Tuff, Basaltic Tuff, Ultramafic Tuff, Folding and Metamorphism, Economic Importance