Dust clouds are a new feature introduced in Generation V alongside rustling grass, rippling water and flying Pokémon shadows. They can be found in several caves throughout Unova.

If you walk into a dust cloud, you'll either find a Gem, Evolutionary Stone, or encounter a rare Pokémon. Gems can only be found this way in Black and White, though some gems can be found on the ground in their sequels. They can also help out your Pokémon in battles by powering up their moves with the right gem.

List of Gems

Bug Gem	Dark Gem	Dragon Gem	Electric Gem	Fighting Gem	Fire Gem
Flying Gem	Ghost Gem	Grass Gem	Ground Gem	Ice Gem	Normal Gem
Poison Gem	Psychic Gem	Rock Gem	Steel Gem	Water Gem

Pokémon

Pokédex	Pokémon	Sprite	Type	Location
#529	Drilbur			Wellspring Cave, Chargestone Cave, Mistralton Cave, Twist Mountain
#530	Excadrill			Challenger's Cave, Victory Road, Giant Chasm