Materials and hardness: What is considered the hardest naturally occurring substance on Earth in standard general-knowledge contexts? Answer based on conventional Mohs hardness scale used in examinations. Choose the correct substance.

Given data

• Asks for the hardest naturally occurring substance on Earth.

Concept/Approach
On the conventional Mohs scale, diamond is rated 10 (the highest). Though some lab or rare phases may approach/exceed diamond in specific properties, standard GK/competitive exams accept diamond as the correct response.

Step-by-step reasoning
Diamond's strong sp³ covalent bonding in a tetrahedral lattice yields exceptional hardness.

Common pitfalls
Choosing dense or precious metals (gold, platinum) which are not the hardest.

Final Answer
Diamond