Enhydro agates are nodules, agates, or geodes with water trapped inside its cavity. Artificial onyx types have also been produced from common chalcedony and plain agates. These agates are typically less colorful, with banded lines of grey and white chalcedony. Enhydro agates are made up of banded microcrystalline or cryptocrystalline quartz. Some wear head or chest ornaments with strings of coral, agates, shells and silver coins. Lake Superior agates have been found in gravel deposits along the Mississippi River basin. Many modern cameos are carved into layered agates. The lava flows formed the conditions for creation of Lake Superior agates. The lava flows formed the conditions for the creation of Lake Superior agates. If silica-rich fluids are able to penetrate into these cavities agates can be formed. The glacier picked up surface agates and transported them south. Very large agates are extremely rare. Most of these agates were from Latin America, in particular Brazil. Enhydro agates can also contain debris or petroleum. Some sticks were marked in agates as well, to aid in newspaper and advertisement composition.