Gypsum: a jewel in Minoan Palatial architecture; identification and characterisation of its varieties.

Gypsum shows a great diversity in crystal morphology and occurs in varieties with quite different macroscopic characteristics. The identification and characterisation of gypsum varieties can be intricate due to surface alteration caused by natural weathering processes or forced dehydration. In this paper we examine the varieties that were used in Minoan Palatial Architecture and their provenance. Petrographic analysis of a series of samples from the sites that used it and the sources, has allowed the detailed classification of the varieties found in the buildings and their corresponding occurrences in the neighbouring outcrops