polished agate, a type of chalcedony that is made up of fine-grained quartz. Agate is known for its unique and colorful banding, which is often created by the deposition of minerals in layers over long periods of time. Polished agate displays a shiny finish, enhancing its beauty and making it a popular collectible for those interested in rocks, fossils, and minerals. It can be used for display specimens or as a decorative piece in any collection of crystals and mineral specimens.