What is the hardest natural substance?
Diamond is the hardest natural substance on Earth. It scores 10, the top of the Mohs scale, and is made of carbon atoms locked in a strong three-dimensional pattern.
Hardness means resistance to scratching. In 1812, German geologist Friedrich Mohs created a simple scale from 1 to 10, ranking minerals by which ones can scratch others. Talc is 1, quartz is 7 and diamond is 10. Only a diamond can scratch another diamond.
Each carbon atom in a diamond is bonded tightly to four others, forming a rigid network in every direction. The same element, carbon, forms soft graphite in pencils, where the atoms are arranged in flat sheets that slide easily over each other.
Hard is not the same as tough
Diamonds are extremely hard but can still chip or shatter if struck at the right angle. Industry uses small diamonds in saw blades, drill bits and polishing tools. Scientists have created a few lab materials and rare forms of carbon that may resist some tests better, but diamond remains the hardest known natural material.
Did You Know?
The Mohs scale is not even. Diamond at 10 is several times harder than corundum, the mineral in rubies and sapphires, which sits at 9.