Quartz is a natural mineral commonly found in rocks with the chemical formula of SiO2. A tetrahedron is a shape involving a central atom surrounded by four outlying atoms that make the general shape of a pyramid. Since SiO2 consists of only three atoms, the oxygen atoms must be shared between two neighboring tetrahedra to form a lattice network of SiO4. So a silicon atom is at the center of the tetrahedron and the four oxygen atoms are at the corners of the pyramid. There are two naturally occurring forms of quartz, alpha and beta. They only real difference between the two is the arrangements of the bonds in three dimensional space.