you can find them underground if u look long enough
yes you can
But if you want a water stone, trade one over from firered/leafgreen on a Pokemon or you can find one in the underground.
you occasionly find them underground
You can find moon stones underground or you have a possibility to find one on a cleffa and clefairy. I hope that helped a little!
If by "stones for Pokemon" you mean Fossils you can find them at the Underground once you have the National Pokedex since most fossils are not of Pokemon that are included in the normal Pokedex: Kabuto, Anorith, Leelip, Omanite, Aerodactile.
all of the stones are obtainable by digging underground
You get the choice if a Turtwig Torchic or a water Pokemon at the start of Diamond
In the desert. (No really, simple logic in the water!)
You can find(fire,sun,water,leaf,andthunder)stones,revives(max revives too),heart scales,everstones,hard stones,(red,blue,yellow,or green)shards,(heat,and icy)rocks,and star pieces
you can find one while mining
you find lumieon in the water in floweroma town the Pokemon that you have to use is butgresse
You can find Pidey in a Pokemon Outbreak in Pokemon Diamond