Yes I've always thought of them as small caves, as techically that is exactly what they are, and have used bits and pieces of cave information in my works with them but when one opens oneself to the vast knowledge that is out there in regards to caves and cultural beliefs surrounding them a whole new world opens. The myths, legends and beliefs surrounding caves come from around the world and are vast. Anyone working with Geodes would do well to look into how caves were looked at in your culture's history and also how caves were looked at by the culture where the geode was found... you may come across some interesting new uses for them. Now I'm not saying this is for everyone but I for one have found a new study project and one that looks to be quite large. There are no books out there that I could find that focus on cave myths or lore but there does seem to be quite a bit of information on the net.

Basic types of Geodes:

1 . thunder eggs: basically it's a volcanic projectile that has cooled fast so that it forms
solid quartz mass inside. Because of different cooling it forms a "rind"
around the quartz-agatized material.

2. Geode: like the thunder egg it is a volcanic projectile , but has cooled more slowly than the thunder
egg and has an air pocket inside. This results is the growth of crystals inside the air pocket. The outside rind cools
quickest, then a material similar to the thunder egg is formed but the cooling is slower to form crystals inside the air pocket.

3. Vug is lava flowing form a volcano (instead of being a projectile )forms air pockets. It could be just air or water that forms the pocket. Due to
the differential cooling caused by the air pocket crystals grow from the
surrounding material and a thin rind is formed from the same material.
Usually the rind material is still super hot forming a glass material. Since
the lava is basalt the rind is a very dark glass. very similar to obsidian.

Vug Geodes or Vug quartz . this is where the cavities are called "vugs" and often are surrounded by massive quartz. When removed from the matrix , the main part can be completely swept away. The "rind" doesn't have to be thick or even exist , although usually there is a least something around the perimeter.



one professor of geology in his circle says there are no hard defined lines seperating vugs, geodes, pockets, crevises or caves. His conclusion are all are caves which are formed differently. Geodes to him implies circular concretions (usually volcanic) with hollows lined by minerals either the same as the outer shell or by different minerals. Vugs to him implies any pocket/crevise or cavity within rock strata or created within a lode by displacing one mineral and gradually filling it with another.