Become a geologist for a day and see what it feels like to break open your own geode. Many of these geodes have hollow centers with crystals. Geodes are formed from fluids which crystallize in cavities within the rounded rock or nodule. Price is per geode.
Put the geode in a bag or old sock (it will probably ruin the bag/sock fyi). Hit it firmly with a hammer aiming for the center. Take care not to hit your fingers. Adult supervision required.