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Topic: Lonsdaleite

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	Lonsdaleite
		Lonsdaleite was first identified from the Canyon Diablo meteorite at Barringer Crater (also known as Meteor Crater) in Arizona in 1967.
		In contrast to the high pressure high temperature (HPHT) cubic diamond growth achieved under hydrostatic pressure, hexagonal diamond was observed to grow when uniaxial pressure was applied to liquid carbon during its solidification.
		Lonsdaleite is fundamentally less stable than diamond, therefore the hardness of lonsdaleite to be slightly less than that of diamond.
	phycomp.technion.ac.il /~anastasy/thesis/node8.html (384 words)

	Lonsdaleite
		Lonsdaleite is a hexagonal polymorph of the carbon allotrope diamond, believed to form when meteoric graphite falls to Earth.
		Lonsdaleite is currently found only in Barringer Crater (also known as Meteor Crater) in Arizona and at Canyon Diablo[?].
		Lonsdaleite is also known as "hexagonal diamond." It has an index of refraction from 2.40 to 2.41, a density from 3.2 to 3.3, and a hardness of 3.00.
	www.ebroadcast.com.au /lookup/encyclopedia/lo/Lonsdaleite.html (85 words)

	NationMaster - Encyclopedia: Lonsdaleite (Site not responding. Last check: )
		Lonsdaleite occurs as microscopic crystals associated with diamond in the Canyon Diablo meteorite; Kenna meteorite, New Mexico; and Allan Hills (ALH) 77283, Victoria Land, Antarctica meteorite.
		Lonsdaleite is also known as "hexagonal diamond." It is transparent brownish-yellow in color and has an index of refraction from 2.40 to 2.41, a specific gravity from 3.2 to 3.3, and a Mohs hardness of 7–8.
		Lonsdaleite is also known as "hexagonal diamond." It is; transparent brownish-yellow in color and has an index of refraction from 2.40 to 2.41, a specific gravity from 3.2 to 3.3, and a Mohs hardness of 7–8.
	www.nationmaster.com /encyclopedia/Lonsdaleite (1332 words)

	Lonsdaleite - The Wordbook Encyclopedia
		Lonsdaleite is also known as "hexagonal diamond." It is transparent brownish-yellow in color and has an index of refraction from 2.40 to 2.41, a specific gravity from 3.2 to 3.3, and a Mohs hardness of 7 - 8.
		The structure of lonsdaleite is very similar to that of diamond in that all atom rings found in the lattice have six member carbon atoms linked only by single bonds with 109.5 degrees between each bond.
		The difference is that not all such six atom carbon rings in lonsdaleite take the form of the chair structure; some rings form in what is called a boat conformation leaving the unbonded distance between non-adjacent carbon atoms smaller than that of the chair structure.
	www.thewordbook.com /Lonsdaleite (552 words)

	Fracture toughening of sintered diamond and carbide ceramics - Patent 4968647
		Lonsdaleite is metastable at room temperature conditions, that is, it tends to convert to graphite.
		Lonsdaleite, which is known per se, exists in meteorites and can be formed synthetically by extremely high load rate (explosive) forming.
		While lonsdaleite is the preferred metastable form of carbon for use herein, it has also been demonstrated that explosively produced diamonds such as those sold by duPont under the trademark "Mypolex" can be used as the toughening agent.
	www.freepatentsonline.com /4968647.html (2576 words)

	Lonsdaleite (Site not responding. Last check: )
		Lonsdaleite je šestiúhelníkový polymorph uhlíku allotrope diamant, věřil k formě když meteorický tuha klesá na Zemi.
		Lonsdaleite je současně najit jen v Barringer kráteru (také známý jako kráter meteoru) v Arizoně a u Canyonu Diablo.
		Lonsdaleite je také známý jak “šestiúhelníkový diamant.” to má index lomu od 2.40 k 2.41, hustota od 3.2 k 3.3, a tvrdost 3.00.
	wikipedia.infostar.cz /l/lo/lonsdaleite.html (91 words)

	Lonsdaleite - Japan
		Lonsdaleite was first identified from the Canyon Diablo meteorite at Barringer Crater (also known as Meteor Crater) in Arizona.
		Lonsdaleite occurs as microscopic crystals associated with diamond in the; Canyon Diablo meteorite; Kenna meteorite, New Mexico; and Allan Hills (ALH) 77283, Victoria Land, Antarctica meteorite.
		Lonsdaleite is also known as "hexagonal diamond." It is; transparent brownish-yellow in color and has an index of refraction from 2.40 to 2.41, a specific gravity from 3.2 to 3.3, and a Mohs hardness of 7–8.
	lonsdaleite.zdnet.co.za /zdnet/Lonsdaleite (700 words)

	Kids.Net.Au - Encyclopedia > Lonsdaleite (Site not responding. Last check: )
		Lonsdaleite is a hexagonal polymorph of the carbon allotrope diamond, believed to form when meteoric graphite falls to Earth.
		Lonsdaleite is currently found only in Barringer Crater (also known as Meteor Crater) in Arizona and at Canyon Diablo[?].
		Lonsdaleite is also known as "hexagonal diamond." It has an index of refraction from 2.40 to 2.41, a density from 3.2 to 3.3, and a hardness of 3.00.
	encyclopedia.kids.net.au /page/lo/Lonsdaleite (110 words)

	lonsdaleite (Site not responding. Last check: )
		Lonsdaleite is also known as "hexagonal diamond." It is transparent brownish-yellow in color and has an index of refraction from 2.40 to 2.41, a specific gravity from 3.2 to 3.3, and a Mohs hardness of 7â“8.
		The difference is that not all such six atom carbon rings in lonsdaleite take the form of the chair structure; some rings form in what is called a boat structure (or more correctly a boat conformation) leaving the unbonded distance between non-adjacent carbon atoms smaller than that of the chair structure.
		A diagram of the structure of lonsdaleite can be viewed here: [1].A diagram of the structure of diamond can be viewed here: [2].
	www.netconferencecall.com /wiki/?title=Lonsdaleite (562 words)

	Lonsdaleite is a hexagon hexagonal polymorph of the carbon carbon... (Site not responding. Last check: )
		Lonsdaleite is a hexagon hexagonal polymorph of the carbon carbon...
		Lonsdaleite is currently found only in Barringer Crater Barringer Crater (also known as Meteor Crater) in Arizona Arizona and at Canyon Diablo Canyon Diablo.
		Lonsdaleite is also known as "hexagonal diamond diamond." It has an index of refraction index of refraction from 2.40 to 2.41, a density from 3.2 to 3.3, and a hardness of 3.00.
	www.biodatabase.de /lonsdaleite (163 words)

	Lonsdaleite
		The difference is that not all such six atom carbon rings in lonsdaleite take the form of the chair structure; some rings form in what is called a boat structure leaving the unbonded distance between non-adjacent carbon atoms smaller than that of the chair structure.
		Frondel, C., U.B. Marvin (1967). "Lonsdaleite, a new hexagonal polymorph of diamond".
		Frondel, C., U.B. Marvin (1967). "Lonsdaleite, a hexagonal polymorph of diamond".
	www.omniknow.com /common/wiki.php?in=en&term=Lonsdaleite (1703 words)

	Kathleen Lonsdale Summary
		In 1966, the "lonsdaleite," a rare form of meteoric diamond, was named for her.
		Lonsdaleite an allotrope of carbon was named in her honour; it is a rare form of diamond found in meteorites.
		A sciences building opened in the 1990s on the University of Limerick campus is named the Kathleen Lonsdale Building in her honour, and there is also a Kathleen Lonsdale Building at UCL.
	www.bookrags.com /Kathleen_Lonsdale (1647 words)

	BBC - h2g2 - Allotropy - Some Familiar Examples
		Lonsdaleite was first identified from 'Meteor Crater' in Arizona in 1967; but has also been identified in other meteorites, including the Allan Hills A77283 meteorite from Antarctica and the Tunguska impact site, Russia.
		Lonsdaleite has a Moh's hardness of 7-8, compared to 10 for diamond.
		Chemists in the USA have recently reported (ca 1995) an allotrope of carbon consisting of long chains of carbon atoms where the alternate carbon-carbon bonds are of different lengths; and consist of C-C bonds and C≡C bonds.
	www.bbc.co.uk /dna/h2g2/A5759517 (2831 words)

	How To Make a Nanodiamond
		In lonsdaleite, however, the planes of chairs are stacked in an AB AB AB sequence, and the carbon-carbon bonds normal to these planes are eclipsed.
		These bond types are classified as sp3 (tetrahedral), sp2 (planar), and sp1 (linear), and are related to the various carbon allotropes including cubic diamond and hexagonal diamond or lonsdaleite (sp3), graphite (sp2), and carbenes (sp1), respectively.
		A crucial decision to be made in a particular application of this invention is the choice of capping group to be used to passivate the two dangling bonds of the C2 dimer that is held by the tooltip molecule.
	www.kurzweilai.net /articles/art0632.html (7451 words)

	diamond engagement ring
		A second form called lonsdaleite with hexagonal (crystal system) crystal system (space group Fd barm) and consist of tetrahedron bonded carbon atoms.
		It is sometimes known as blue ground for the export and import of rough diamonds passed through the top of the art.
		The original model were general guidelines as there were several aspects of diamond (and a distinct mineral species) that crystallizes with hexagonal (crystal system) crystal system (space group Fd barm) and consist of tetrahedron bonded carbon atoms.
	diamond-ring.stardo.org /diamond-engagement-ring.html (854 words)

	World of Carbon
		Natural: It is formed in ultramafic rocks, especially kimberlite breccias, and in detrital sedimentary deposits derived from them, in river and marine placers.
		A rare form of hexagonal "diamond" known as Lonsdaleite is found in certain meteorites, such as those from Canyon Diablo, (USA).
		This octahedral diamond crystal, found in South Africa, is embedded in kimberlite.
	invsee.asu.edu /nmodules/Carbonmod/everywhere.html (406 words)

	The Mysterious Allotropes of Carbon
		Such stacks are found within the structure of hexagonal diamond (lonsdaleite) and are a strong, compact structure.
		Documenting not only cubic and hexagonal (Lonsdaleite) forms of diamond, but also a new metallic phase of carbon, metastable at terapascal pressure, is also discovered at higher pressures (see S. Scandolo et al.).
		Diamond is the hardest material (except, maybe lonsdaleite, the hexagonal polymorph of diamond); graphite is the softest...
	dendritics.com /scales/c-allotropes.asp (1758 words)

	NOVA Online \| The Diamond Deception \| Diamonds in the Sky
		But analysts studying the Canyon Diablo diamonds found that up to a third of them bore a hexagonal atomic structure never before seen in diamond.
		Mineralogists named the new hexagonal variant of diamond lonsdaleite after the British mineralogist Dame Kathleen Lonsdale, who helped advance the study of natural diamond crystals.
		Microscopic diamonds appear to have formed in the fiery instant when the meteor that created Arizona's Canyon Diablo struck the Earth.
	www.pbs.org /wgbh/nova/diamond/sky.html (879 words)

	IngentaConnect First-principles study on the lonsdaleite phases of C, Si and Ge (Site not responding. Last check: )
		Crystalline C, Si and Ge in a lonsdaleite (hexagonal diamond) structure are studied by plane-wave pseudopotential calculations in the scheme of density-functional theory and the local density approximation.
		The theoretical bulk modulus of lonsdaleite C is 0.2-0.3% higher than diamond.
		Considering the exchange-correlation energy correction, it is estimated that lonsdaleite Ge is a semiconductor with a small direct band gap.
	www.ingentaconnect.com /content/iop/jphyscm/2003/00000015/00000012/art00102 (216 words)

	Science NetLinks: Carbon: Structure Matters
		Finally, students should look up lonsdaleite in the Mineralogy Database. This is a rare, hexagonal polymorph of diamond, believed to be formed when meteoric graphite falls to earth.
		Lonsdaleite is thought to be extraterrestrial in origin.
		Have students draw a flow chart in which they explain what happens to the graphite molecule when lonsdaleite is formed.
	www.sciencenetlinks.com /Lessons.cfm?DocID=154 (901 words)

	Lonsdaleite . Barringer Crater . New Mexico . Earth . Tunguska
		The great heat and stress of the impact transforms the graphite into diamond, but retains graphite s hexagonal crystal lattice.
		Lonsdaleite is also known as "hexagonal diamond." It is transparent brownish-yellow in color and has an refractive index index of refraction from 2.40 to 2.41, a specific gravity from
		Nature: 214: 587-589 Frondel, C. Marvin 1967, Lonsdaleite, a hexagonal polymorph of diamond, Am.Min.: 52
	www.uk.kunsimuna.net /Lonsdaleite_UK_973799_rz (654 words)

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