Variety of volcanic sand with burnt granules resembling powdered brick: it is a siliceous or siliceous and aluminous material which, when mixed with hydraulic limes and water, becomes a cement-like compound capable of setting under water. It was used in Antiquity. Artificial pozzolan was made by calcining fire clay and adding lime, sand, and water, with fine brick dust.
Gwilt (1903);N i (1835);W. Papworth (1852);Sturgis et al. (1901–2)