A geode is a geological secondary formation that types inside sure sedimentary and volcanic rocks. Composed primarily of agate, geodes are hole or partially hole and include a cavity lined with crystals or crystal formations. Geodes generally type in cavities inside volcanic rocks akin to basalt and rhyolite, however they may also be present in sedimentary rocks like limestone and sandstone.
Geodes are shaped when minerals, carried by groundwater, seep right into a cavity within the rock and regularly crystallize. The crystals develop inward from the partitions of the cavity, ultimately filling it fully. The most typical minerals present in geodes are quartz, calcite, and amethyst, though different minerals, akin to pyrite, celestite, and barite, may also be discovered.