Selenite

Selenite (Gr. Selēnē, 'the moon'). This name is given to the transparent variety of Gypsum (q.v.). It occurs in distinct crystals belonging to the oblique or monoclinic system, or in folia. It is usually white (colourless), but sometimes it is tinged with red, yellow, green, gray, &c. Selenite is soft, easily cut, and capable of being split into very thin plates. These are much used in polarising apparatus (see POLARISATION). Selenite is a comparatively common mineral, although it rarely occurs in large quantities. Finely crystallised specimens are found at Bex in Switzerland, in Sicily, and at different places in the United States. There is a magnificent group of crystals of this mineral in the British Museum from Reinhardbrunn in Gotha. In Nova Scotia, where, in the vicinity of Oxford, near River Philip, there are vast deposits of gypsum (large quantities of which are sent to the United States), selenite is found abundantly. At Petitcodiac, New Brunswick, where extensive deposits of gypsum also occur, there is a vein of nearly pure selenite one mile long and eight feet wide. Selenite, being a pure form of gypsum, is used for making the finest kind of plaster of Paris. Plates of selenite are said to have been used by the ancients for some of the purposes for which we use glass.