Boron carbide(B4C) is black crystal with metallic luster with hardness only second to diamond, higher than silicon carbide. Its Mohs hardness is 9.3 with stable chemical property and wiith relative density 2.52, melting point 2350℃,and boiling point higher than 3500℃.Boron carbide is stable in dilute acid solution. When heated to 1000℃, it is slowly oxidized to carbon dioxide and boron oxide in oxygen. Boron carbide has high thermal neutron capture capability and good resistance to abrasion.It is used to process precious stones, ceramics, molds, tools and bearings. It is also used as nozzles, bulletproof materials and etc.