Hypertext Webster Gateway: "tufa"
From Webster's Revised Unabridged Dictionary (1913) (web1913)
Tufa \Tu"fa\, [It. fufo soft, sandy stone, L. tofus, tophus. Cf.
{Tofus}, {Toph}, and {Tophin}.] (Min.)
(a) A soft or porous stone formed by depositions from water,
usually calcareous; -- called also {calcareous tufa}.
(b) A friable volcanic rock or conglomerate, formed of
consolidated cinders, or scoria.
From WordNet (r) 1.7 (wn)
tufa
n 1: a soft porous rock consisting of calcium carbonate deposited
from springs rich in lime [syn: {calc-tufa}]
2: hard volcanic rock composed of compacted volcanic ash [syn:
{tuff}]
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