lonsdaleite
Sign in to saveAlso known as IMA1966-044
Lonsdaleite (named in honour of Kathleen Lonsdale), also called hexagonal diamond in reference to the crystal structure, is an allotrope of carbon with a hexagonal lattice, as opposed to the cubical lattice of conventional diamond. It is found in nature in meteorite debris; when meteors containing graphite strike the Earth, the immense heat and stress of the impact transforms the graphite into diamond, but retains graphite's hexagonal crystal lattice. Lonsdaleite was first identified in 1967 from the Canyon Diablo meteorite, where it occurs as microscopic crystals mixed in with ordinary diamon
Key facts
- Mineral.name
- Lonsdaleite
- Mineral.image
- Lonsdaleite.png
- Mineral.caption
- Crystal structure of lonsdaleite
- Mineral.formula
- C
- Mineral.IMAsymbol
- Lon
- Mineral.strunz
- 1.CB.10b
- Mineral.system
- Hexagonal
- Mineral.class
- Dihexagonal dipyramidal (6/mmm) H-M symbol: (6/m 2/m 2/m)
- Mineral.symmetry
- P63/mmc
- Mineral.unit cell
- a = 2.51 Å, c = 4.12 Å; Z = 4
- Mineral.color
- Gray in crystals, pale yellowish to brown in broken fragments
- Mineral.habit
- Cubes in fine-grained aggregates
- Mineral.mohs
- 7–8 (for impure specimens)
- Mineral.luster
- Adamantine
- Mineral.diaphaneity
- Transparent
- Mineral.gravity
- 3.2
- Mineral.opticalprop
- Uniaxial (+/−)
- Mineral.refractive
- n = 2.404
via Wikipedia infobox
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Encyclopedic overview
9 sectionsContents
- Hardness
- Chemical properties
- Occurrence
- Manufacture
- Scams
- See also
- References
- Further reading
- External links
Lonsdaleite (named in honour of Kathleen Lonsdale), also called hexagonal diamond in reference to the crystal structure, is an allotrope of carbon with a hexagonal lattice, as opposed to the cubical lattice of conventional diamond. It is found in nature in meteorite debris; when meteors containing graphite strike the Earth, the immense heat and stress of the impact transforms the graphite into diamond, but retains graphite's hexagonal crystal lattice. Lonsdaleite was first identified in 1967 from the Canyon Diablo meteorite, where it occurs as microscopic crystals mixed in with ordinary diamond.
It is translucent and brownish-yellow and has an index of refraction of 2.40–2.41 and a specific gravity of 3.2–3.3. Its hardness is theoretically superior to that of cubic diamond (up to 58% more), according to computational simulations, but natural specimens exhibited somewhat lower hardness through a large range of values (from 7–8 on Mohs hardness scale). The cause is speculated to be due to the samples having been riddled with lattice defects and impurities.
Excerpted from Wikipedia’s “lonsdaleite” article, available under the CC BY-SA 4.0 licence.