Well, I can only guide you to a leaf stone. (is it the same or not) In Castelia City, a guy will ask you what monkey (from the guy in the dreamyard) you got. Say pansage, you get a leaf stone, panpour, you get some kind of water stone etc.
a grass Pokemon
Go to black city and gain people from pokemon white's white forest who gives you the option of selling leaf stone. After, save, go to the market that just appeared in your city and buy (expensive) leaf stones.
the light stone isn't in Pokemon white only the dark stone in white and the light stone in black
Nuzleaf into Shiftry
in eterna forest
In the grass
You have to see grass and then go in the grass and battle. It is usually Elekid for me but try to get a Pokemon in White Forest. If there is no grass then you can't catch Elekid and other Pokemon so just try to get grass. :)
you don't. you only get the dark stone
It is found underground.
You can get one in Viridian Forest.
most grass Pokemon like sunkern to sunflora.
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.