My son got a geode kit for Easter and today was the day we got into it. When I say a geode kit, it's really just some geodes, googles, and some informational booklets. To break open geodes you need some hardware, which isn't included. You can do it with just a hammer, but it doesn't break terribly nicely. The better way to do it is with a chisel. We started with a mallet, but you really need an actual hammer.
It's important to tap lightly. It might feel like you're not getting anywhere, but if you hit too hard, the geode will shatter. This happened to the first one he opened.
It pained me to watch him hit a rock with a chisel, but since I knew it was coming I gave him my most beat up chisel for the job. Sure enough, by the end of the session the chisel was terribly blunted. But once he's done with cracking all of them, it should sharpen back up nicely.
Here's the result of his work. 3 geodes opened up.
