Boron carbide, also known as black diamond, is an organic substance with a molecular formula of B₄C, usually gray-black fine powder. It is one of the hardest materials known (the other two are diamond and cubic boron nitride). It is used in tank armor, bulletproof vests and many industrial applications. Its Mohs hardness is 9.3.

Boron carbide (B4C), also known as black diamond, has a molecular formula of B₄C, usually gray-black powder. It is one of the hardest materials known in armor, bulletproof vests and many industrial applications. Its Mohs hardness is 9.5. It was a by-product of metal boride research in the 19th century and was not scientifically studied