Tufa

Tufa is a variety of limestone, formed by the precipitation of carbonate minerals from ambient temperature water bodies. Geothermally heated hot-springs sometimes produce similar (but less porous) carbonate deposits known as travertine. Tufa is sometimes referred to as (meteogene) travertine; care must be taken when searching through literature to prevent confusion with hot spring (thermogene) travertine. Calcareous tufa should not be confused with tuff, a porous volcanic rock with parallel etymological origins.