These transluscent stones always appear to have several colors swirling within them. They have few practical uses, and as such are of relatively little interest to the general populace.
To mages, however, they have interesting possibilities. A single fae stone can amplify a spell, making it much more powerful than it would ordinarily be – The scope of amplification, depends on the size of the stone. As a general rule, at least. Using a stone in this manner, however, turns it completely black and it will crumble to nothing within seconds.
The final known use for these stones, comes in their powdered state. The power is burned into a rune, thus activating the magic inherent in the rune. As such, they are neccesary for enchanting purposes.
So far, fae stones have been mined in the few caverns discovered to hold them. It is unknown why or how they appear there.