Lonsdaleite is an allotrope of carbon, first discovered in 1967 in the Canyon Diablo meteorite crater in Arizona. Named after the British crystallographer Dame Kathleen Lonsdale, who identified its unique hexagonal crystal structure. It can be up to 58% harder than diamond under ideal conditions.
However, due to its rarity, it is not used as frequently as other materials, such as cubic boron nitride or synthetic diamonds, which are also incredibly hard but easier to obtain and work with commercially.
Lonsdaleite forms when the carbon atoms in graphite are subjected to extremely high pressures, such as those that occur during a meteorite impact. Therefore, it is typically found in the remains of meteorite impact sites, such as the Canyon Diablo meteorite crater in Arizona. However, due to its rarity, it has only been found in a few locations on Earth and is not known to exist in significant quantities anywhere in the universe.