Chalcedony is composed of two types of silica minerals and is semi-transparent to translucent. In its broad sense, Chalcedony refers to a wide variety of gemstones, such as agate, Aventurine, carnelian, Chrysoprase and Chrysocolla.
Chrysoprase, which means golden leek, goes from apple green to deep green and consists of microscopic crystals (=cryptocrystalline) and nickel, the latter being responsible for its color. It is one of the oldest known gemstones and is sometimes confused with jade.