Diamonds have another challenger for the hardest substance title.
A team of scientists at Rice University in Houston worked out the mathematical formula behind carbyne, a specific arrangement of lowly carbon atoms.
Carbyne is created when carbon atoms are linked together as a chain of sequential double bonds or alternating single and triple bonds. Carbyne is believed to be twice as hard as a carbon sheet and will need more energy to break than a diamond.
Its other distinguishing property is its behavior, which changes according to materials it connects with. For instance, if you add a methylene molecule to the otherwise hard substance, it will become malleable.
Carbyne has been seen in space, in asteroids and interstellar debris, but is hard to replicate in a lab. The longest chain created is a little more than 40 atoms long.
This is still fairly untested and therefore volatile. The math says combustion isn't spontaneous meaning carbyne could interact with air at room temperature safely.