Bag of geodes

While appearing to be a regular bag, this bag is of similar properties to that of the bag of holding, with one significant difference. Instead of being able to put items in, you can take out some shiny black stones. They appear to be regular stones, and act like them too, however once the command word is spoken, every stone outside of the bag will explode with roughly the amount of force in order to break a simple stone wall, though enough could do much more. The bag can hold a maximum of 20 of these stones, which magically return when exploded.