The amorphous structure of glassy silica in two-dimensions. No long-range order is present; however there is local ordering with respect to the tetrahedral arrangement of oxygen (O) atoms around the silicon (Si) atoms. Note that a fourth oxygen atom is bonded to each silicon atom, either behind the plane of the screen or in front of it; these atoms are omitted for clarity.
Silica is a white or colorless mineral composed of silicon dioxide (SiO2). It occurs commonly as quartz and sand, and in many other familiar rocks and minerals, including flint, granite, amethyst, and rock-crystal. Silica is refractory and inert, though it dissolves in hydrogen fluoride and reacts with bases to form silicates. It is used to make glass, ceramics, concrete, and carborundum.