Summarize this article in one sentence.
Look for medium-sized rocks that appear to be more round than surrounding rocks. Geodes look a lot like normal rocks but can sometimes have an egg-like shape that distinguishes them. Sharp, pointy rocks rarely contain geodes. Look for rocks that have a unique, bumpy texture on the exterior. Geodes are rarely perfectly smooth.  The texture of a geode’s exterior may have a cauliflower-like appearance. Inspect the surface for any signs of minerals inside. Sometimes traces of the inside crystals are visible on the surface. Pick up the rock and assess its weight. If the rock feels lighter than that surrounding rocks, it may be a geode. Geodes have a hollow space inside, which is what allows the crystals to form. You can also shake the rock next to your ear to test whether it is hollow. You may hear small pieces of rock or crystal rattling around inside if it is hollow.

Summary:
Look for round rocks. Check the surface for bumps. Test whether the rock has a hollow interior.