2006ApJ...653L.153G

The first complete infrared FTIR absorption spectra of carbonado diamond confirm the interstellar origin of this most enigmatic diamond. All previous attempts failed to measure the absorption of carbonado diamond in the most important IR range of 1000-1300/cm (10.00-7.69 µm) because of silica inclusions. In our investigation, KBr pellets were made from crushed silica-free carbonado diamond, and thin sections were also prepared. The 100-1000 times brighter synchrotron infrared radiation permits a greater spatial resolution. Inclusions and pore spaces were avoided and/or sources of chemical contamination were removed. The FTIR spectra of carbonado diamond mostly depict the presence of single nitrogen impurities and hydrogen. The lack of identifiable nitrogen aggregates in the infrared spectra, the presence of features related to hydrocarbon stretch bonds, and the resemblance of the spectra to CVD and presolar diamonds indicate that carbonado diamonds formed in a hydrogen-rich interstellar environment. This is consistent with carbonado diamond being sintered and porous, with extremely reduced metals, metal alloys, carbides, and nitrides, light carbon isotopes, surfaces with glassy melt-like patinas, deformation lamellae, and a complete absence of primary, terrestrial mineral inclusions. The 2.6-3.8 billion year old fragmented body was of asteroidal proportions.