Hematite Ring

There was a flash and when Jon looked back the rock was gone. In its place was a ring, with a gem set into it, just like a diamond. But this wasn't a diamond. It was a black gem called hematite.  Jon put it on and tested it. "I wish that my hair would be blonde for the next ten seconds." Nothing happened. But when Jon touched the black gem on the ring and made his wish again, it worked. And after ten seconds, Jon's hair changed back to its normal brown color.