Diamond
Natural stone
Pure carbon, the hardest natural stone. It can still chip on a hard knock along its cleavage, and it can burn in a flame without flux protection.
Hardness (Mohs): 10
Natural stone
Pure carbon, the hardest natural stone. It can still chip on a hard knock along its cleavage, and it can burn in a flame without flux protection.
Hardness (Mohs): 10