Agate
Agate is the name given to numerous varieties of banded Chalcedony, a mineral of the Quartz family. Its name comes from the Achetes River in Sicily, where Agates were first found. Usually banded in layers, or stripes, some varieties have "eye" markings, or specks of color, some have fossilized inclusions, and others are solid.
There are hundreds, if not thousands of types of agates.