A geode is a crystal or rock formation that contains a cavity that is lined with crystals or other mineral matter. For each of these geodes there is another half somewhere else in the world, because when they are found they look like little rocks. It is not until they are carefully cut in half and polished that you can see the wonders within. Looking inside is like looking into another world. It is quite acceptable to buy more than one as they all have their own characters.