Roll On, Pokémon!

Ash and friends stumble across a valley where a girl named Rochelle uses Donphan to harvest Amberite, a gemstone only found in this valley. Ash, Misty, and Brock follow her as she makes her rounds, and see exactly how she finds it. However, Team Rocket hears about the gemstone and decides to steal a Donphan so that they can find their own Amberite.