what is agate?
For other uses, see Agate (disambiguation). Agate /ËÃ¦É¡Ét/ is a cryptocrystalline variety of silica, chiefly chalcedony, characterised by its fineness of grain and brightness of color. Although agates may be found in various kinds of rock, they are classically associated with volcanic rocks and can be common in certain metamorphic rocks.