Agate (from Greek agates) is a mineral whose name derives from the historical name of the Achates River (now Dirillo) in Sicily. It is a concentrically fine and coarse layered variety of chalcedony (quartz). Strictly speaking, agate is not a mineral but a mixture of strips of quartz, chalcedony and opal. A characteristic, eye-visible feature of agate is the colorfulness; the most common colors are white-gray, pale blue, orange-red and black. On the Mohs hardness scale it has a hardness degree of 6-7. We know several varieties of agate such as pseudoachate, moss agate (dendritic texture), coral agate, ruined agate, lightning agate and others. In the middle of the agate there are sometimes cavities usually filled with amethyst crystals, smoky quartz, calcite or zeolites. The resulting coloration of the agate then depends on the amount of so-called inclusions of other minerals or admixtures of other elements in the structure. Some agates can also be dyed artificially - it has already been done in ancient Greece and Rome. Individual characteristic drawings of stones then have their own names.