Taken by themselves, geodes are gorgeous, with the insides lined with crystals that add a sense of beauty and wonder to the rocks, and they become even more amazing when they are dinosaur eggs, as was ...

Amethyst geodes—some stretching 5 m long—dot the ancient lava flows of Uruguay’s Los Catalanes mining area. The geodes contain calcite, colorless quartz, and agate, another quartz mineral. Large ...