Spectroscopic study of impurities and associated defects in nanodiamonds   from Efremovka (CV3) and Orgueil (CI) meteorites
  The results of spectroscopic and structural studies of phase composition and of defects in nanodiamonds from Efremovka (CV3) and Orgueil (CI) chondrites indicate that nitrogen atomic environment in meteoritic nanodiamonds (MND) is similar to that observed in synthetic counterparts produced by detonation and by the Chemical Vapour Deposition (CVD)-process. Most of the nitrogen in MND appears to be confined to lattice imperfections, such as crystallite/twin boundaries and other extended defects, while the concentration of nitrogen in the MND lattice is low. It is suggested that the N-rich sub-population of MND grains may have been formed with high growth rates in environments rich in accessible N (i.e., N in atomic form or as weakly bonded compounds). For the first time the silicon-vacancy complex (the "silicon" defect) is observed in MND by photoluminescence spectroscopy. 
A.A. Shiryaev, A.V. Fisenko, I.I. Vlasov, L.F. Semjonova, P. Nagel, S.   Schuppler
cond-mat.mes-hall astro-ph.SR