Scientists created a pure hexagonal diamond in the lab, confirming a long-debated carbon structure slightly harder than natural diamonds.

Diamonds are famous for their strength, but scientists have long suspected that another form of diamond might be even harder.

Diamonds form deep within the Earth's mantle, around 250 kilometers below the surface, where immense pressure (up to 10 GPa) and temperatures (around 2,200 °C) compress carbon into diamonds over ...