You don't. There's no such thing as a ground stone
you don't. you only get the dark stone
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 find a secret place you find a legenary pokemon that holds this stone defeat it you get it.
there is no "electric stone" but there is a thunder stone witch can be found under ground
route 6
find a sun stone.
You find it in the chargestone cave
in pokemon black and white
you can find them under ground or there is one in sunyshore city.
it is a cheat
The Black Stone is on display at Nacrene City's museum.
To find a shiny stone you can trade a pokemon thats holding the shiny stone or maybe someone in your pokemon game will give you one. If you use a Shiny Stone on Minnico it will evolve into Cinnico