Chergach (H5) Meteorite - 26.8g Stone
Collected fresh after it fell from space, this is a beautiful, and nicely sized stone that features a jet-black fusion crust on majority of the surface, with amazingly fresh, grey matrix peeking out through a few small windows.
History: In fall and winter of 2007, meteorites were collected in the Erg Chech region of Mali, north of Taoudenni. Nomads reported the stones fell after a smoke cloud was seen and several detonations were heard over a wide area during daytime July 2-3 2007. The original finder of the first meteorites was Mr. Ouled Bleila, who died in a car accident on his way back from the trip to the Chergach strewn field in October 2007. According to the Tuareg people from Algeria who visited the fall site in September 2007, the elliptical strewn field stretches for more than 20 km in a northeasterly direction.
Physical characteristics: A large number of fusion-crusted stones have been recovered, the largest ones are 17.8kg and 13.9 kg, the smallest ones about 1.5 g.
Petrography: (E. Gnos, MHNGE; B. Hofmann, NMBE, M. Eggimann, UBE/NMBE) Mean chondrule size is 0.38 mm (n = 61). Mean size of plagioclase grains is ~20 μm. Troilite is polycrystalline, rich in silicate inclusions, and shows diffuse boundaries to metal. Some metal is rich in silicate- and troilite inclusions. No Cu metal observed. Shock stage is S3, some shock veins are visible, no weathering (W0). In addition to this dominant lithology, a significant number of stones consist of chondritic clasts (H5 S3-4 W0, identical to the homogeneous lithology) set in a fine-grained, black, silicate impact melt matrix with abundant droplets of metal and metal-troilite. Shock stage of small clasts is up to S4.
Mineral compositions and geochemistry: Olivine Fa18.2 (chondrite fragments in impact melt are Fa18.4), pyroxene Fs15.5 Wo1.2 (fragments in impact melt are Fs16.0, Wo1.4).
Cosmogenic radionuclides: (Patrick Weber, Particle Physics Group, Institute of Physics, University of Neuchâtel) Gamma-spectroscopy performed in November, 2007 showed the presence of the following short-lived radionuclides: 46Sc, 56Co, 54Mn, 58Co, 7Be, 57Co, 22Na, 60Co, 26Al. Recalculated to July, 2007, 22Na was 44.0 ± 1.1 dpm/kg and 26Al 20.8 ± 0.8 dpm/kg. The 22Na/26Al activity ratio of 2.1 is consistent with a fall in July, 2007 and demonstrates that this material is not identical with Bassikounou.
Scale cube shown for scale and not included.