Silicates

The silicates constitute the largest and most common class of minerals. They are translucent, at least in thin splinters, and on the average are lower in specific gravity and harder than most minerals. Water is present in a number of them, especially in the zeolites, where it is loosely bound. In other varieties, water is strongly held and cannot be removed without destroying the mineral. Regardless of their complex nature, silicates all contain the silicate atomic structure, whose fundamental building block is the tetrahedron, in which one silicon atom in the center is surrounded by four equally spaced oxygen atoms. The structure of the tetrahedron corresponds to the four-sided tetrahedron in the isometric crystal system. The number and manner of linking of the silicon-oxygen tetrahedrons are the basis upon which the different silicate structures are formed.