väga suure kõvadusega keemiline ühend B4C, mida toodetakse booroksiidist (B2O3) süsinikuga taandamise teel elektriahjudes, rakendusteks abrasiivtöötlusel, tehnokeraamika tootmiseks jms, very hard material (third only to diamond in hardness) B4C, produced by reduction of boric oxide (B2O3) by carbon in an electric arc furnace; employed as an abrasive in grinding wheels, belts, papers, powders, in articles of high resistance to abrasion etc