TUFA

n. kind of porous limestone deposited by springs and streams

This article is about the geological formation. For the Xianbei clan that was active during China's Sixteen Kingdoms period, see Southern Liang.Tufa is the name for an unusual geological form of calcite rock.Tufa is a rough, thick, rock-like calcium carbonate deposit that forms by precipitation from bodies of water with a high dissolved calcium content. Tufa is not to be confused with tuff which is volcanic.
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Noun
1. a soft porous rock consisting of calcium carbonate deposited from springs rich in lime
(synonym) calc-tufa
(hypernym) rock, stone
2. hard volcanic rock composed of compacted volcanic ash
(synonym) tuff
(hypernym) volcanic rock

v. swell, increase in volume, expand, inflate; increase in intensity or amount

A soft or porous stone formed by depositions from water, usually calcareous; -- called also calcareous tufa.

  

A friable volcanic rock or conglomerate, formed of consolidated cinders, or scoria.