Quartz: A homogenous solid formed by a repeating, three-dimensional pattern of atoms, ions, or molecules and having fixed distances between constituent parts.
Quartz Crystal Structure:
Quartz is silicon dioxide, SiO2, consisting of one part silicon and two parts oxygen. In spite of its simple binary composition, X-ray diffraction (XRD) investigations show quartz has a complex atomic structure. This complicated structure is comprised of silicon atoms, which lie on three inrterpenetrating hexagonal lattices, with the oxygen atoms grouped in a tetrahedral manner around the silicon atoms.
The most basic structural unit of quartz, and all silicate minerals, is the (SiO4) tetrahedral configuration. In SiO2, each oxygen atom is shared with two silicon atoms; the (SiO4) tetrahedra share each of their corner oxygen atoms and form a three-dimensional network. The three interpenetrating hexagonal lattices of silicon atoms have a spiral arrangement in the vertical direction in respect to each other. This complex, vertical, helical atomic structure is manifested by various forms of twinning and by the handedness of quartz.