Stone
The substances which enter into the composition of simple stones are silica, alumina, zirconia, glucina, lime, magnesia, etc., and the oxides of iron, manganese, nickel, chromium, and copper; and it is seldom that more than four or five of these substances are found combined in one stone. (See SILICA; SANDSTONE; ROCK; etc.) Artificial stone is produced by the cementing properties of soluble alkaline silicates on sand. Sand 10, glass 1, clay 1, silicate of soda 1, is brought to the consistency of putty in a pug-mill; this is moulded, dried, kilned at a red heat, and allowed to cool, thus forming a vitrified mass similar to sandstone. A later method produces the stone without baking by effecting a double composition with the silicate of soda and the chloride of calcium. See SOLUBLE GLASS.