you find them in caves in poke balls on the floor or the thunder stone can be found in the solacen ruins insinde a rock hidden
You can find stones undergrounds.
A few stones can be found elsewhere but majority is underground ( NO TRADE STONES )
There are two ways to evelove Pokemon in Pokemon platinum by lefstones and leveling up.
Iron Island.
The Underground
there is none sorry
Togetic into Togekiss and Roselia into Roserade
You can find stones Underground. You take the explorer kit and then go underground.
the same way as platinum
Underground. Use Explorer Kit, then dig around.
You can find shiny stones on route 228 and Iron island
i dont know if u can do this in platinum, but u can always go underground... if not, resort to a cheat code.