CaSO4 . A naturally occurring mineral of anhydrous calcium sulphate that is often found in gypsum deposits. Anhydrite was first identified as a mineral in deposits at Innsbruck, Austria. Anhydrite can be transparent or translucent and has a lustrous sheen. It occurs in several colours such as white, grey, blue, pink, red and lavender. Anhydrite was used in ancient Egypt for carved objects and vessels, many of which are in the shape of animals (Fay, 1998). It is used in the manufacture of Portland cement to control the set. Synonyms: blue marble; calcium sulphate. Museum of Fine Arts, Boston (2000); RS Means Building Glossary (undated). [J. Cassar, R. de Angelis]