Onix

“As it grows, the stone portions of its body harden to become similar to a diamond, but colored black.”

— Pokémon Red

“Burrows at high speed in search of food. The tunnels it leaves are used as homes by DIGLETTs.”

— Pokémon Yellow

“It twists and squirms through the ground. The thunderous roar of its tunneling echoes a long way.”

— Pokémon Gold