Chalcedony

Chalcedony is a cryptocrystalline form of silica. Its standard chemical structure is that of Quartz (SiO2 (silicon dioxide)).  It can be semitransparent to translucent and has a waxy luster.  It is found in  several different forms, including onyx, agate, and jasper. It is said to impart mental flexibility and improve memory. It is also thought to bring feelings optimism and improve self-perception.