Calcareous tufa

Firebrick was the dominant furnace material from about 5000 bc to the 1950s. Many years ago, man discovered that tufa (calcareous sinter, or solidified bubbled lava) is an excellent insulating material for high-temperature furnaces (maybe as in this book s frontispiece). Modern insulating firebrick is a manmade equivalent of tufa. 

Duckstein, m. calcareous tufa, duff, a. dull, dead. 

Stoneware, composed of plastia clay from the Palatinate, ground quartz from Oberwald or Bern-cast e, calcareous tufa from Stork. The glaze contains lead, and the waie has ft yellow tint. 

Calcification and deposition of carbonates in rivers are uncommon but may be found in some stagnant parts, and in the upper reaches, when the deposits may occur as calcareous tufas, travertines, and sinters (Golubic, 1967,1973). In some rivers, oncoids and algal balls are formed. 

Baker, A. Simms, M.J. (1998) Active deposition of calcareous tufa in Wessex, UK, and its implications for the late-Holocene tufa decline . The Holocene 8, 359-365. 

Rieger, T. (1992) Calcareous tufa formations. Searles Lake and Mono Lake. California Geologist (for 1992), 45, 99-109. 

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