What is the hardest rock on earth?

The hardest naturally occurring rock on Earth is diamond. Diamond is composed of carbon atoms arranged in a crystal lattice structure, making it incredibly hard and resistant to scratching. It has a Mohs hardness scale rating of 10, which is the highest possible rating. Diamonds are primarily found in kimberlite pipes or as alluvial deposits in rivers and streams. They are used in jewelry, cutting tools, and industrial applications due to their hardness and durability.