Nanodiamond Sources Nanodiamonds in the

Nanoscale diamonds were discovered in 1987 by Lewis et al.[5] in meteorites. Not all meteorites contain diamonds. At this time, nanodiamonds have been found in specific types of meteorites, the so-called ''carbonaceous chondrites.'' Two major sources of nanodiamonds are the ''Allende'' chondrite (C3V type), which weighed several tons when it fell on Mexico in 1969, and also other types of chondrites, such as the Murchison meteorite (type C2).

The nanodiamonds found in these meteorites have a lognormal size distribution, with a median diameter of 26 A, corresponding to roughly 1060 atoms. The shape of the distribution has been interpreted to be caused by growth followed by partial conversion of small grains to larger ones. The particles were shown to contain impurities, mainly hydrogen, nitrogen, and oxygen, principally in -COOH groups.[6] It is worth noting that in some cases, such as C2-type chondrites, a diamond (in its nanoscale form) is up to five times

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