Would like to either see the magic stone have one of the following:
-More Health
-Repairable
-Invulnerable (and have chance for large biters if invulnerable).

Otherwise freaking love it. One other option is for the stone to be a chest and to spawn random items in the chest so that you can keep checking back from time to time instead of having to just waste time mining it.

I was just playing with the code and it seems like adding the line "destructible = false" makes for perfect interaction with the stone as even if it gets attacked, it goes back to full health.