After Diamond, Cubic Boron Nitride and Boron Oxide, Hot pressed Boron Carbide has the highest hardness known. Its main applications make use of its excellent wear resistance and high strength. It has a low density but a high elastic modulus and high compressive strength, which leads to its use as a ballistic material. 20% of natural boron is the €^OB isotope, giving Boron Carbide a high neutron capture cross section. It is therefore used in neutron-absorbing applications, such as shielding. Boron carbide has good resistance to acids but not to alkali hydroxide melts.