Heartscales allow you to teach a forgotten move to your pokemon.It helps if you need to re-evaluate your pokemons moves.Just give it to a move tutor,they vary from game to game.
eat hearts
i do not think you can but you can take Pokemon to the heartscale guy and see if that move is compatible with any of your Pokemon you give him a heartscale that you find under ground he collects them
you mine under ground but its small and looks like a rainbow
By going underground and digging.
go to the move maniac in pastroia city with a heartscale
They are usually found on the ground by using the Itemfinder/Dowsing Machine.
Underground. You have to dig at dig spots to find them, among other things.
None of the Pokemon do, silly! :D you get the heartscale by digging it from the underground. (be careful, their small!! if you go to pastoria, there is a guy who will teach your Pokemon a forgotten move if you give him a heartscale. his house is next to the lake.) *hope this helped*
Dig for it underground. Its rare but it is possible to dig one up
You can find them on Luvdisks in Pokemon Emrald and Ruby and Sapphire, and you find them underground in Pokemon diamond
It is used for the move tutor, who teaches you Pokemon old moves that they have forgotten.
Mistralton City the house next to the entrance for a heartscale