What is the stone in a wizards staff?

[Inziladun]

Originally Posted by Axbolt

In the hobbit Radagast the brown uses the stone from his staff to draw evil from the sick hedgehog, and for the first time I noticed that in the films all the wizards (Radagast, Gandalf, Saruman) seem to have a “stone of power” in there staff, it made me wonder what the significance of this might be, if there is any?

Welcome, Axbolt!

My guess is that they might be the kidney stones passed by Christopher Tolkien when told of the liberties taken by filmmakers with The Hobbit.

Actually, I haven't seen those movies, so I don't know if that might have been mentioned in a deleted scene, perhaps.