A geode is a geological secondary formation that kinds inside sure sedimentary and volcanic rocks. Composed primarily of agate, geodes are hole or partially hole and comprise a cavity lined with crystals or crystal formations. Geodes generally kind in cavities inside volcanic rocks equivalent to basalt and rhyolite, however they will 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 steadily crystallize. The crystals develop inward from the partitions of the cavity, ultimately filling it utterly. The commonest minerals present in geodes are quartz, calcite, and amethyst, though different minerals, equivalent to pyrite, celestite, and barite, will also be discovered.