A rosy red volcanic clay that has been used as a pigment and a component in cement. Pozzolana is mined in Italy at Pozzuoli near Naples. It is has been used since ancient times by the Romans. Pozzolana is mixed with lime to form pozzolana cement. It dries slowly but forms a strong surface. Similar cements contain trass and Santorin earth. Pozzolana was also a popular pigment for fresco paintings because it dried quickly to a hard impenetrable surface like cement. Synthetic pozzolanas are made from slag, burnt clay, HTI powder (a ceramic material “high temperature insulation”), PFA (pulverised fuel ash) and powdered bricks. Synonyms: terra di pozzuoli; Pozzuoli red; pozzuolana; gaize cement; puzzolan cement; Santorin cement; silikat-cement; tarras cement; trass cement. Ashurst (1983); Museum of Fine Arts, Boston (2000). [J. Cassar, R. de Angelis]