Rare mystery diamonds came from outer space, scientists report

[pesco]

Originally published at: Rare mystery diamonds came from outer space, scientists report | Boing Boing

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[theophrastus]

IANAM (i am not a mineralogist) yet…

Called lonsdaleite, these space diamonds has a hexagonal structure rather than the cubic structure of a typical diamond.

diamonds are composed entirely of carbon in a beautiful cubic array. graphite is composed entirely of carbon in a hexagonal planar array. That is, a pure carbon compound symmetry group, for example ‘cubic’, determines the name, diamond, we give the substance and other physical properties. All by way of my head-scratch: “space diamonds has a hexagonal structure” sounds like they’re graphite. …which i’ll presume is wrong somehow [shrug emoji]

[Richard_Kirk]

Suppose we have a hexagonal raft of carbon atoms (not graphite, yet) we call A. Suppose we stack a second raft B on top of the first, fitting in the gaps between the atoms in layer A. There is third possible position we can call C with the atoms sitting in the other gaps that B did not occupy.

If you stack these planes ABCABC… you get the close-packed cubic diamond structure. If you stack the planes ABABAB you get the hexagonal structure with one hexagonal inversion symmetry axis instead of four for the FCC structure. This probably needs some strong shock conditions to reduce the symmetry, but the bonds are the same as for diamond, and the material properties are probably similar.

Graphite is something else. In graphite, the bonds lie entirely in the plane of the sheets,. The sheets are weakly bonded by Van de Waals forces, and can slip over each other.

[Brainspore]

Oddly when they first announced their findings about these cool new space crystals that reporter from the Daily Planet suddenly got really queasy and had to excuse himself from the press conference.