Lonsdaleite Properties and Structure
- Allotrope of carbon with a hexagonal lattice
- Translucent and brownish-yellow in color
- Refractive index of 2.40-2.41
- Specific gravity of 3.2-3.3
- Hardness theoretically superior to cubic diamond
- Hexagonal unit cell with interlocking rings of six carbon atoms
- Some rings are in the boat conformation
- Bonds between layers are in the eclipsed conformation
- Predicted to be 58% harder than diamond on the 100 face
- Natural specimens exhibit a range of hardness values
Formation of Lonsdaleite
- Formed when graphite in meteorites undergoes immense heat and stress
- Retains graphite's hexagonal crystal lattice
- First identified in the Canyon Diablo meteorite
- Microscopic crystals associated with ordinary diamond
- Synthesized in the laboratory by compressing and heating graphite
- Lonsdaleite is formed by shock compression of graphite.
- Nanosecond formation of diamond and lonsdaleite has been observed in laboratory experiments.
- Shock-compressed graphite can transform into hexagonal diamond in nanoseconds.
- Polycrystalline aggregates of diamond with lonsdaleite have been found in Yakutian placers.
- Evidence from central Mexico supports the Younger Dryas extraterrestrial impact hypothesis.
Occurrence of Lonsdaleite
- Found in meteorites such as Canyon Diablo, Kenna, and Allan Hills 77283
- Naturally occurring in non-bolide diamond placer deposits in the Sakha Republic
- Claims of Lonsdaleite in sediments at Lake Cuitzeo are uncertain
- Presence in local peat deposits linked to the Tunguska event
- Disputed claims of Lonsdaleite in the Greenland ice sheet
Manufacture of Lonsdaleite
- Produced by compressing and heating graphite in a static press or using explosives
- Chemical vapor deposition can also produce Lonsdaleite
- Thermal decomposition of poly(hydridocarbyne) can yield Lonsdaleite
- Accidental discovery of room temperature Lonsdaleite production using a diamond anvil cell
- Creation of large Lonsdaleite crystals with lasers, although they are destroyed shortly after
- Lonsdaleite can be synthesized through chemical vapor deposition.
- Hexagonal diamond formation has been observed from dissolved carbon in nickel.
- Hexagonal diamond synthesis has been achieved on strained films.
- Poly(hydridocarbyne) can be synthesized as a precursor to diamond and diamond-like ceramics.
- Electrochemical polymerization can be used to form poly(hydridocarbyne) for diamond production.
Discovery, Identification, and Properties of Lonsdaleite
- Lonsdaleite was first discovered in meteorites.
- It was named after Dame Kathleen Lonsdale, an Irish crystallographer.
- Confocal Raman spectroscopy can be used to observe the formation of hexagonal diamond.
- Lonsdaleite has been identified in the Greenland ice sheet.
- New evidence suggests that the Tunguska cosmic body was of meteoritic origin.
- Lonsdaleite is a form of diamond with a hexagonal crystal structure.
- It is considered to be harder than cubic diamond.
- Lab-made hexagonal diamonds have been found to be stiffer than natural cubic diamonds.
- Lonsdaleite has potential applications in high-pressure experiments and as an abrasive material.
- The properties of lonsdaleite make it a valuable material for scientific research.
Lonsdaleite Data Sources