Trass
TRASS noun A volcanic earth, resembling puzzolana, used as a cement; or a coarse sort of plaster or mortar, durable in water, and used to line cisterns and other reservoirs of water. The Dutch tarrass is made of a soft rock stone found near Collen, on the lower part of the Rhine. It is burnt like lime, and reduced to powder in mills. It is of a grayish color.