tuff
A relatively soft volcanic rock made from consolidated erupted material, used as a textured natural facade stone.
Tuff is a relatively soft, highly textured rock formed from material ejected in a volcanic explosion. While its components vary, it generally consists of hardened volcanic ash mixed with various sediments released in the explosion along with pieces of molten rock or glass. Because of its easy workability it has been valuable since ancient times as a building material. Its variegated textures can make it aesthetically appealing as a cladding material.
The facade consists of the consolidated natural rock. Its fragments and ash can produce an uneven or varied texture across the cut surface.
Suevite can have a similar appearance, but forms through an impact rather than a volcanic eruption. Appearance alone does not establish the rock type.