Diamond Stone

From the Super Mario Wiki

The Diamond Stone is a stone shaped like a diamond in Paper Mario. Along with the Lunar Stone and the Pyramid Stone, Mario and his friends need this stone to gain access to Tutankoopa's tomb in the Dry Dry Ruins.

It can be found in a secret chamber, guarded by two Stone Chomps. It fits into the Chomp Rock statue.

Artifacts

Artifact | Balance Stone | Beanstar | Black Chest | Black Skull | Chaos Heart | Chomp Rock | Cobalt Star | Crystal Ball | Crystal Stars | Diamond Stone | Form Baton | Grand Star | Green Power Star | Jade Raven | Lost Mushroom | Lunar Stone | Magic Scepter | Magical Map | Marvelous Compass | Moon Stone | Music Key | Power Star | Pulse Stone | Pure Heart | Pyramid Stone | Red Power Star | Sacred Cylinder of Cheese | Shadow Star | Shine Sprite | Silver Star | Skull Gem | Star | Star Piece | Star Rod | Sun Stone | Treasures | Vibe Scepter | Volcano Vase