To misquote a famous song, "Diamonds are industry's best friend." Cubic diamond is the hardest mineral on Earth and is used in everything from precision cutting tools to high-performance semiconductors as well as expensive jewelry. But there is a rare and potentially tougher form called hexagonal diamond (HD), which has long been the subject of theories and debate over its actual existence. But now researchers from China claim to have created this elusive form of carbon in the lab.