Agate is the name given to numerous varieties of banded chalcedony, a mineral of the Quartz group. Like other Quartz minerals, Agate have trigonal crystal structure and a hardness of 7. Stones such as Moss Agate and Dendritic Agate, because they do not exhibit banding, are not Agates in the strictly scientific sense, but they will be considered here as well.
The name Agate comes from the river Achetes in Sicily, where Agates were found in ancient times. Agates have been discovered with the artifacts of Neolithic people, and they were used by the early Egyptians before 3000 B.C.