A geode is a geological secondary formation that varieties 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 comparable to basalt and rhyolite, however they may also be present in sedimentary rocks like limestone and sandstone.
Geodes are fashioned 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, finally filling it utterly. The commonest minerals present in geodes are quartz, calcite, and amethyst, though different minerals, comparable to pyrite, celestite, and barite, may also be discovered.