Geodes are geological rock formations which occur in sedimentary and certain volcanic rocks. Geodes are essentially rock cavities or vugs with internal crystal formations or concentric banding. The exterior of the most common geodes is generally limestone or a related rock, while the interior contains quartz crystals and/or chalcedony deposits. Some geodes are completely filled with crystal, being solid all the way through. Store for Knowledge carriers a number of geode related gifts including, break your own geodes, single break your own geodes, bulk pack geodes, thunder eggs, cut geodes, whole unopened geodes, crack open geodes, tumbled geodes, moracon geodes, mexico geodes, geode activities, sliced geodes, polished geodes, amethyst geodes, ocos geodes, and many more. We sell geodes from all over the world inlcuding Mexico, U.S., Brazil and Africa. Break your own geodes are great for teachers and students. The bulk packs are great for small and large school groups. They make a great geology lesson.