How did the Blarney Stone get its magical powers?

there're not some. The novel talks about magic. so it's full of magic. dummy

it is in Blarney Castle

If you mean fictionally...x-ray vision, heat vision, super strength, super speed, and the power to veto any law and overpower a two thirds vote in Congress! Also, there is levitation, speed, power...

every one. but only a gifted few can hone their magical powers into ultimate power like Ryan the Bruce, conqueror of ancient Antarctica and who tamed the penquins.

You can just look at it or more commonly you can do the traditional thing and kiss it.