Tufa
Tufa
[Italian fufo soft, sandy stone, Latin tofus, tophus. Compare Tofus, Toph, and Tophin.]
(a)
(Mineralogy) A soft or porous stone formed by depositions from water, usually calcareous; -- called also calcareous tufa.
(b)
(Mineralogy) A friable volcanic rock or conglomerate, formed of consolidated cinders, or scoria.