In 2001, cubic boron carbonitride of BC 2 N composition (c-BC 2 N) was synthesized at high pressure -high temperature conditions . The new phase possesses Vickers hardness of 76 GPa which make it the second after diamond hardest material. At ambient pressure in an inert atmosphere c-BC 2 N remains stable up to 1800 K, and, thus, is characterized by significantly higher thermal stability than polycrystalline diamond.