Boron carbide (chemical formula approximately B4C) is an extremely hard boron–carbon ceramic material used in tank armor, bulletproof vests, and numerous industrial applications. With a Mohs hardness of about 9.497, it is one of the hardest materials known, behind cubic boron nitride and diamond.

B4C can be mirror polished and has a very good resistance to acids. It is refractory and chemically inert. However, it is less resistant to oxidation than Silicon Carbide.

Boron Carbide Production methods:
Hot pressing and Hot isostatic pressing are good means for producing such a ceramic.
B4C is fully dense and has a pure single phase shape.

Hot pressing has the inconvenient of limiting the available sizes and shapes that could be produced.
B4C is machined with diamond tools.