trass

A light-colored tuff used in hydraulic cement.

An earthy or more or less compact rock, made up in large part of firmly comminuted pumice or other volcanic material.

A white to gray volcanic tufa, formed of decomposed trachytic cinders; — sometimes used as a cement. Hence, a coarse sort of plaster or mortar, durable in water, and used to line cisterns and other reservoirs of water.

A white to grey volcanic tufa, formed of decomposed trachytic cinders, sometimes used as a cement.

A coarse sort of plaster or mortar, durable in water, and used to line cisterns and other reservoirs of water.