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Lonsdaleite is an allotrope sometimes called "hexagonal diamond", formed from graphite present in meteorites upon their impact on the earth. The great heat and pressure of the impact transforms the graphite into a denser form similar to diamond but retaining graphite's hexagonal crystal lattice. "Hexagonal diamond" has also been synthesized in ...
In mineralogy, amorphous carbon is the name used for coal, carbide-derived carbon, and other impure forms of carbon that are neither graphite nor diamond.In a crystallographic sense, however, the materials are not truly amorphous but rather polycrystalline materials of graphite or diamond [2] within an amorphous carbon matrix.
Coal is very rich in carbon (anthracite contains 92–98%) [64] and is the largest commercial source of mineral carbon, accounting for 4,000 gigatonnes or 80% of fossil fuel. [ 65 ] As for individual carbon allotropes, graphite is found in large quantities in the United States (mostly in New York and Texas ), Russia, Mexico, Greenland, and India.
It is an allotrope of carbon in the form of a plane of sp 2-bonded atoms with a molecular bond length of 0.142 nm (1.42 Å). In a graphene sheet, each atom is connected to its three nearest carbon neighbors by σ-bonds , and a delocalized π-bond , which contributes to a valence band that extends over the whole sheet.
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.
Diamond and graphite are two allotropes of carbon: pure forms of the same element that differ in crystalline structure.. Allotropy or allotropism (from Ancient Greek ἄλλος (allos) ' other ' and τρόπος (tropos) ' manner, form ') is the property of some chemical elements to exist in two or more different forms, in the same physical state, known as allotropes of the elements.
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Graphite (/ ˈ ɡ r æ f aɪ t /) is a crystalline allotrope (form) of the element carbon. It consists of many stacked layers of graphene , typically in the excess of hundreds of layers. Graphite occurs naturally and is the most stable form of carbon under standard conditions .