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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.
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 ...
From theoretical considerations, lonsdaleite is expected to be harder than diamond, but the size and quality of the available stones are insufficient to test this hypothesis. [9] In terms of crystal habit , diamonds occur most often as euhedral (well-formed) or rounded octahedra and twinned , flattened octahedra with a triangular outline.
Lonsdaleite, an allotrope of carbon, was named in her honour; it is a rare harder form of diamond found in meteorites. [41] [42] Several universities have names buildings in her honour including at University College London, at the University of Limerick, [43] and at Dublin City University, [44] and Maynooth University.
When viewed all together, the atomic positions are the same as in lonsdaleite (hexagonal diamond). Each atom is tetrahedrally coordinated. The structure can also be described as an HCP lattice of zinc with sulfur atoms occupying half of the tetrahedral voids or vice versa.
Amethyst crystals – a purple quartz Apophyllite crystals sitting right beside a cluster of peachy bowtie stilbite Aquamarine variety of beryl with tourmaline on orthoclase Arsenopyrite from Hidalgo del Parral, Chihuahua, Mexico Aurichalcite needles spraying out within a protected pocket lined by bladed calcite crystals Austinite from the Ojuela Mine, Mapimí, Durango, Mexico Ametrine ...
This list includes those recognised minerals beginning with the letter L.The International Mineralogical Association is the international group that recognises new minerals and new mineral names; however, minerals discovered before 1959 did not go through the official naming procedure, although some minerals published previously have been either confirmed or discredited since that date.
See also External links A Abelsonite: C 31 H 32 N 4 Ni – American physicist Philip Hauge Abelson (1913–2004) Abswurmbachite: Cu 2+ Mn 3+ 6 O 8 SiO 4 – German mineralogist Irmgard Abs-Wurmbach (1938–2020) Adamite: Zn 2 AsO 4 OH – French mineralogist Gilbert Joseph Adam (1795–1881) Agrellite: NaCa 2 Si 4 O 10 F – English optical mineralogist Stuart Olof Agrell (1913–1996 ...