Lonsdaleite, the hexagonal diamond, could aid industry

A new study claims to have discovered why the ultra-hard space diamond was found inside a ureilite meteorite.

The Australian research supports the notion that the diamond originated from the mantle of a destroyed inner solar system dwarf planet. It also suggests that the method of formation is akin to chemical vapor deposition and could be used for industrial applications.

The researchers say ‘In these meteorites, folded graphite crystals have been pseudomorphed by lonsdaleite. This occurred at mildly elevated pressures through reaction between graphite and supercritical C-H-O-S fluids. Ongoing reaction during cooling then promoted partial replacement of lonsdaleite by diamond + graphite. This process is akin to industrial chemical vapor deposition but operates at higher pressure (∼1–100 bar) and provides a pathway toward manufacture of shaped lonsdaleite for industrial application.’

Lonsdaleite itself was found in the Canyon Diablo iron meteorite in the US 1967. Officially, it is an individual mineral species. The new research appeared in PNAS yesterday.