Polished Agate Slice

Agate is a translucent variety of microcrystalline quartz. Agate generally forms by the deposition of silica from groundwater in hollow cavities of volcanic rocks. The coloration of agates is due to other minerals present in the silica.

Agate has also been known to fill veins or cracks in volcanic rock. Such agates, when cut transversely, exhibit a succession of parallel line giving a banded appearance to the section. Such stones are known as banded agate, riband agate and striped agate.