Petrography and Chemical Analysis
All the mineralogical and petrographic testing has been done at the University of Bern, Switzerland and the Museum of Natural History, Switzerland by the skilled team of E. Gnos, B. Hofmann and M. Eggiman. These are their results:
« Electron microprobe analysis yielded olivine Fa18.6, pyroxene Fs16.3 Wo1.1, plagioclase An13.7. Mean olivine composition determined by XRD is Fa17.3. Mean chondrule size 0.35 mm (n=53). Metal abundance is 8 vol%, troilite 6.6 vol%. Mean size of plagioclase grains is ~20 mm. Troilite is polycrystalline, rich in silicate inclusions, and shows diffuse boundaries to metal. Metal is partly rich in silicate- and troilite inclusions. Rare metallic Cu (10 mm) at kamacite-taenite boundaries and in troilite. Shock stage is S2, some shock veins are visible, no weathering (W0). »
The cosmogenic radionuclides measured by Patrick Weber from the Particle Physics Group, Institute of Physics, University of Neuchâtel are consistent with a recent fall in October 2006: « Gamma-spectroscopy performed in December-January 2006 showed the presence of the following radionuclides: 48V, 46Sc, 56Co, 54Mn, 58Co, 7Be, 51Cr, 57Co, 22Na, 26Al and 60Co. Recalculated to 12 October 2006 22Na was 38.0±2.2 dpm/kg and 26Al 31.5±2.1 dpm/kg, the activity ratio of 1.21 is fully consistent with a fall on that date.»
There is however a slight inconsistency between the dates of October 12 resulting from these measurements and the fall date of October 16 as announced in the local press and as declared in the eyewitness accounts. This inconsistency may be within the tolerance of the gamma-spectroscopy data obtained.
The classification of the Bassikounou meteorite as submitted to the NomCom is that of an ordinary chondrite (H5), with a shock stage of S2 showing no weathering (W0).
Prior to the Bassikounou event, a total of eight meteorites plus two crater structures were known for Mauritania. Among those are six finds and only two falls. Aioun el Atrouss, a diogenite weighing 1000gm fell at Gounquel in south-east Mauritania on April 17 in 1974. Kiffa, an ordinary chondrite of a TKW of 1500gm fell on October 23, 1970 at 14:55hrs. Bassikounou, the third registered fall in Mauretania is by far the largest and best documented fall in the history of the country.