These whole, unopened geodes are an exciting addition to any earth science, geology, or rock & mineral unit. Sorted by density, many are hollow and can be easily split open, using an ordinary hammer, to reveal a variety of crystal formations within. Students love opening these, then trading the pieces to begin their own rock collections. Our favorite way to split them is to put one in an old sock, then strike it with a hammer outside. This keeps all the pieces together while protecting bystanders from any fragments. Remember to wear your safety goggles. Sold in packages of 6.