tufa

noun

1. (countable, uncountable)Calcareous lime deposited by precipitation from a body of water, such as a hot spring.

   “B.J. Szabo presented the results of a survey of the tufa mounds that border Pyramid Lake indicating that uranium-series methods can be used to approximate the ages of such tufa deposits. In the Pyramid Lake Basin, tufas less than 50,000 years old contain large quantities of excess thorium, and the error in age estimates made using uranium-series methods is not small enough to confirm results from ¹⁴C determinations.”

   “Resedimented tufas also contribute where erosion has washed detritus from other hillside tufa deposits.”

   “The tufas at Tianshengqiao have different shapes in different development stages and in different structural sections.”

2. (countable, uncountable)A variety of volcanic rock, tuff.

   “1825, "Oliver Oldschool" (Joseph Dennie), John Elihu Hall (editors), The Port Folio, page 426, This again is followed by a bed of stony tufa of a reddish colour, containing fragments of a spongy lava, amphigone, pyroxene, mica, and common lava; and, like the former, traversed by argillaceous veins.”