You have to dig underground.
Here are SOME stones: dawn dusk leaf fire sun water oval stone everstone (prevents Pokemon from evolving) moon thunder these are all of the stones i know about.
Thunder stones, Water stones, Fire stones, Leaf stones, Shiny stones, Dusk stones, Oval stones, Moon stones, Sun stones.
Ryan8or- Yes you can get it in the giant store
Well, this may not be helpful, but Fire stones evolve some fire Pokemon... Sun stones also evolve fire Pokemon, (Fire stone, Thunder stone and Water stone also evolve "Eevee", the Pokemon you get after completing sinnoh dex.
the only two i know are: poliwhirl eevee so yeah :p improve my answer if anyone knows any more.
The evolution stones in Diamond/Pearl/Platinum are the water stone, fire stone, thunder stone, moon stone, leaf stone, sun stone, dusk stone, shiny stone, and dawn stone. (Sorry if I missed one) And even though this is the opposite answer, the stone to keep Pokemon from evolving (with or without evolution stones) is the everstone. Hope this helps! :)
You can get a Seel in Pokemon Pearl by finding it in the water on route 226.
Fire Stone: Obtain on Tuesdays in Pokeathlon Athlete Shop. Water Stone: Obtain on Wednesdays in Pokeathlon Athlete Shop. Thunderstone: Obtain on Thursdays in the Pokeathlon Athlete Shop. (All for 2500 points) Other Stones: Obtain from being First Place in Bug Catching Contest, which are held on Tuesdays, Thursdays, and Saturdays.
blastoise is the best
Water and grass
You cant
With a water type pokemon.