Alabaster, the name frequently given to two different mineral substances - the one a sulphate of lime, a pure variety of gypsum, and the other a carbonate of lime, of the same chemical composition as most of the marbles. It was used with the same ambiguity by the ancient Greeks and Romans. The resemblance of the two substances is in their delicate white color and fine grain. Each is easily carved and susceptible of a fine polish. They might well in ancient times have passed as varieties of the same substance: the gypsum alabaster being more delicate and softer to cut, and requiring much more care to polish; the calcareous alabaster more firm, and better adapted for the sculpture of larger figures. The latter was frequently obtained from the drippings of the water in limestone caves, which holds carbonate of lime in solution, and deposits it in the form of stalactites and stalagmites. These by a little ingenuity were made to take the forms of the mould the waters dripped upon; or the natural stalagmites of the purest colors were selected, and then wrought into the desired figures. - The name alabaster, now properly limited to the gypseous variety, is derived from the town Alabastron, the site of which is believed to have been between the Red sea and the Nile in Middle Egypt. Here the stone was extensively wrought into boxes and pots for precious ointments and perfumes.

A white granular gypsum, pure and in sound blocks, is quarried in Siena and in other places in Tuscany, and manufactured in Florence, Leghorn, Milan, and Volterra, into utensils similar to those used of old, as well as into vases, lamps, clock stands, etc. They are exported from these places in considerable quantity to the United States. The composition of this alabaster is 46.3 per cent, sulphuric acid, 32.9 lime, and 20.8 water. Its hardness is 1.5-2 of the mineralogical scale. It soon tarnishes on exposure to the air, and is easily injured by dust and smoke. Articles made of it should be kept under a glass cover.