Chalcedony is known as cryptocrystalline form of silica, fashioned of very fine intergrowths of quartz and moganite. These are both silica minerals, but they differ in that quartz has a trigonal crystal arrangement, while moganite is monoclinic. Chalcedony’s standard in a chemical structure (based on the chemical structure of quartz) is SiO2 (silicon dioxide).
Chalcedony has a glistening luster and may be semitransparent or translucent. It can expect a wide array of colors, but those most generally seen are white to gray, grayish-blue, or a variation of brown ranging from pale to nearly black. The color of chalcedony deceived commercially is often enhanced by dyeing or heating.
The name chalcedony comes from the Latin chalcedonius (alternatively spelled calchedonius). The name appears in Pliny the Elder’s Naturalis Historia as a designation for a translucid kind of Jaspis. The name is probably derived from the town Chalcedon in Asia Minor. The Greek word khalkedon also appears in the Book of Revelation. It is an hapax legomenon discovered nowhere else.