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This is a follow-up study of a work by Kramers et al. (2013) on an unusualdiamond-rich rock found in the SW side of the Libyan Desert Glass strewn field.This pebble, called Hypatia, is composed of almost pure carbon. TransmissionElectron Microscopy and X-ray diffraction results reveal that Hypatia is madeof defect-rich diamond containing lonsdaleite and deformation bands. Thesecharacteristics are compatible with an impact origin on Earth and/or in space.We analyzed concentrations and isotopic compositions of all five noble gasesand nitrogen in several mg sized Hypatia samples. These data confirm thatHypatia is extra-terrestrial. The sample is rich in trapped noble gases with anisotopic composition close to the meteoritic Q component. 40Ar/36Ar ratios inindividual steps are as low as 0.4. Concentrations of cosmic-ray produced 21Necorrespond to a nominal cosmic-ray exposure age of ca. 0.1 Myr if produced in atypical m-sized meteoroid. Such an atypically low nominal exposure age suggestshigh shielding in a considerably larger body. In addition to the Xe-Qcomposition, an excess of radiogenic 129Xe (from the decay of extinct 129I) isobserved (129Xe/132Xe = 1.18 +/- 0.03). Two N components are present, anisotopically heavy component ({\delta}15N = +20 permil) released at low temp.and a major light component ({\delta}15N = -110 permil) at higher temp. Thisdisequilibrium in N suggests that the diamonds in Hypatia were formed in space.Our data are broadly consistent with concentrations and isotopic compositionsof noble gases in at least three different types of carbon-rich meteoriticmaterials. However, Hypatia does not seem to be related to any of thesematerials, but may have sampled a similar cosmochemical reservoir. Our studydoes not confirm the presence of exotic noble gases that led Kramers et al. topropose that Hypatia is a remnant of a comet that impacted the Earth.

A comprehensive study of noble gases and nitrogen in Hypatia, a diamond-rich pebble from SW Egypt