Agate is the banded form of chalcedony (pronounced kal-ced-on-ee; cryptocrystalline quartz) and its name was derived from the site of its discovery, the river Achates (now Dirillo) in southwest Sicily. The main conditions necessary for agate formation are the presence of silica from devitrified volcanic ash, water from rainfall or ground sources, manganese, iron and other mineral oxides that form the white, red, blue, grey, brown or black bands. . Agate comes in many different forms ranging from semitransparent to opaque. But a few of the agate varieties are blue agate, blue lace agate, crazy lace agate, green agate, Indian agate, moss agate, fire agate, tree agate, onyx, sardonyx and wood agate.