A pale stone, blue chalcedony sometimes has a dark internal form with bands of blue and white and often has a colorless streak. Chalcedony, a group term for a smooth form of quartz, has a waxy or greasy luster, can be dull or transparent to translucent and is composed of microscopic fibers. The extreme hardness of quartz minerals in the blue agate helps distinguish them from minerals of lesser hardness, which they sometimes resemble.
Chalcedony is found in many deposit forms. Stalactite growths of the mineral are seen in numerous places and often assume fantastic shapes and forms. Chalcedony also may replace materials such as wood.
As a gemstone, blue agates are often used to make jewelry. The blue agate can be found in Oglala National Grasslands in northwestern Nebraska.