CaSO4.2H2O. A kind of gypsum made of transparent and translucent scales (“scaglie”). This mineral was known and used during the antiquity under the name of “lapis specularis” because of the translucent, mirror-like surface. Selenite and sericolite, both occurring in the Appennino Emiliano in Italy, were defined/called scagliola in the seventeenth century in Italy. The selenite was put in an oven at 300°C until it was broken and could be ground with mortar and pestle into powder that was then sieved. Adding water and animal glue produced a thick paste that could be coloured. Wittenburg (1999). [J. Cassar, R. de Angelis]