Quartz is a simple form of silicate, and has the chemical formula for silicon dioxide, SiO2. It is found abundantly in the surface of the Earth, and its properties include a density of about 2.65 grams per cubic centimetre, an index of refraction of about 1.54 or 1.55 and a hardness of about seven. The hardness of a chemical compound is measured on the Mohs hardness scale. It is only when a silica-rich compound occurs in its most natural and purest form in the cavities and fractures that are formed under the Earth's surface (which is the only place where the compound can grow unrestricted), that a crystal-clear form of quartz will be formed. All quartz crystals are hexagonal in shape and appear to have a natural symmetrical pattern formed by the natural and uninhibited growth. The symmetry of the crystal lattice is reflected by the smooth planar surface, but it does not represent its cleavage planes.
