Everlasting
Everything stays.
Though that does raise the question of dialga's typing. If dialga were the diamond pokémon, shouldn't it be rock type, considering power gem is a rock type move and diamonds are referred to as "rocks"?
A pearl is a gem as well, so your theory doesn't work. Dialga's typing (Steel) is actually visible through its body, while Palkia has no physical part hinting its Water type. See ?