You can find them in the underground, they're kinda rare. Also, i think there a few "invisible" ones around, like in rocks that have items in them but i don't remember where they are.

I think you mean Wood Hammer.

Heart Scales can be dug up Underground, found using the Dowsing Machine Poketch App (usually near beaches, shallow water, and shoals), or (if you have the National Dex) fish for Luvdisc (they hold Heart Scales 50% of the time) outside Pokemon League HQ using the Super Rod* and Thief/Covet them away.

* 60% chance of Gyarados (Level 30-55), 35% chance of Octillery (Level 30-55), 5% chance of Luvdisc (Level 20-30)

You can get heart scales from the guy in solacean town as long as you bring him the pokemons he wants to see.

Thanks for the reminder, jafar0892.

Heart Scales can be:
--Dug up Underground
--Found using the Dowsing Machine Poketch App (usually near beaches, shallow water, and shoals)
--Show the Manager at the Solaceon Newspaper the Pokemon he wants for the article and he'll give you one plus some random Pokeballs (Timer, Dusk, etc.)
--If you have the National Dex, fish for Luvdisc (they hold Heart Scales 50% of the time) outside Pokemon League HQ using the Super Rod (appears 5% of the time) and Thief/Covet them away.

Its is easy to find them when diging

Underground.... There are tons of them....