What is the hardest natural substance on Earth?

Diamonds are the hardest natural substance on Earth due to their unique crystal structure, which is composed entirely of carbon atoms arranged in a tetrahedral lattice formation. This arrangement allows diamonds to withstand significant pressure and resist scratching, making them the most durable material known in nature. The strength of the carbon bonds in a diamond's structure contributes to its hardness, which is rated as a 10 on the Mohs scale of mineral hardness, the highest possible rating.

In comparison, substances like gold, iron, and quartz have different atomic structures that do not provide the same level of hardness. Gold is a soft metal, iron is significantly weaker and more malleable, and quartz, while hard, typically ranks around 7 on the Mohs scale. Thus, diamonds stand out distinctly as the hardest material, making them invaluable in various applications, including industrial cutting tools and jewelry.