A cryptocrystalline version of silica, chalcedony is composed of very fine ingrowths of quartz and morganite. It gets its name from the town of Chalcedon in Turkey, and the name appears in Pliny the Elder's Naturalis Historia as a term for a translucid form of jaspis (jasper). Chalcedony has many varieties that go by different names, such as agate, carnelian, chrysoprase, heliotrope, and onyx. This purple variety leans more periwinkle, and is incased in its matrix, similar to boulder opal (another silica based mineral). Polished on one side and raw on the other, this specimen makes a fine cabinet piece for collectors.