You find it in N's castle after you beat the elite four.
black stone
find them
in pokemon black and white
You can only find a Magma Stone in Pokemon Black 2, White 2, Pokemon Diamond, Pearl, and Platinum. It is not available in Pokemon Black and White.
You can find a Shiny Stone in route 6.
The Black Stone is on display at Nacrene City's museum.
route 1
route 1
You can find it in the outside area or relic castle
if you mean, a light ball, then catch a pikachu at the safari zone
it is in the desert near relic castle
A worker gives it to you in Shopping Mall Nine.