Rocks and Minerals Information Sheet R003
Agate is form of Chalcedony, which has a fine microcrystalline structure characteristically displaying brightly coloured, thin parallel bands that follow the contours of the cavity in which it formed.
Chalcedony is itself a variety of silica which is often translucent or partially transparent.
Sometimes the cavities are not completely filled with the solidified silica gel, and frequently in these cases the centres may contain crystals of amethyst, rock crystal or smoky quartz.
Agates were prized by the people of ancient Sumeria and Egypt, where it was used to produce ornaments, receptacles, amulets and charms.
Agate is much used in carved formations to produce wonderful cameos and intaglios.
Many specimens produce amazing images which can look like sea and landscapes, the colours vary enormously and they are receptive to being unnaturally coloured.