7–8 Mohs (natural impure); up to 58% harder than cubic diamond theoretically
density
3.51 g/cm³
Core Principles & Analysis
First identified in 1966 in the Canyon Diablo iron meteorite crater in Arizona and named in honor of pioneering British X-ray crystallographer Dame Kathleen Lonsdale.
Whereas cubic diamond stacks sp³ carbon layers in an ABCABC sequence where all C–C bonds are staggered, lonsdaleite stacks layers in an ABAB hexagonal wurtzite sequence with eclipsed C–C bonds along the c-axis.
First-principles simulations predict that defect-free lonsdaleite can withstand 58% higher indentation stress (~152 GPa) than cubic diamond, and micrometer-sized hexagonal diamond crystals have been synthesized in diamond anvil cells above 100 GPa.