Lunar (feldspathic melt breccia)
History: One stone was found by Luc Labenne in the desert at night.
Physical characteristics: The 128.8-g meteorite lacks an obvious fusion crust. The interior consists of a gray, vesicular (up to 1.2 mm vesicles) melt matrix with rounded clasts stained red by hematite. Many vesicles are filled with terrestrial alteration products, including calcite, Ca-sulfate, and celestite.
Petrography: (R. Zeigler, WUSL) Melt matrix dominated by plagioclase (average: An96.7Or0.2) with intergrown of pigeonite (average Fs50Wo27; Fe/Mn = 57), augite (Fs60Wo27; Fe/Mn = 48), and olivine (Fo61; Fe/Mn = 102) in an apparent poikilitic texture. Also present within the matrix are small grains of troilite, Cr,Ti,Fe spinel (19 wt% TiO2, 25 wt% Cr2O3 , 23 wt% FeO), and ilmenite (5 wt% MgO, 1.5 wt% Cr2O3), the latter two often intergrown. There are a few plagioclase clasts (typically 0.2 mm, up to ~1 mm) and a few smaller olivine and pyroxene clasts. Large veins of partially devitrified shock melt occur. Average composition of the shock-melt vein: 43.7% SiO2, 0.24% TiO2, 29.7% Al2O3, 4.3% FeO, 0.07% MnO (Fe/Mn = 63), 4.0% MgO (Mg´ = 63), 16.8% CaO, 0.32 wt% Na2O, and 0.03 wt% K2O.
Geochemistry: Bulk Chemistry: (R. Korotev, WUSL): 0.32% Na2O, 4.1% FeO, 7.9 ppm Sc, 140 ppm Ni, 1.2 ppm Sm.
Classification: Achondrite (lunar, impact-melt breccia).
Specimens: 20.1 g are on deposit at WUSL, the main mass is held by Labenne.
It’s the only lunar meteorite to have been found at night! Compositionally, Shişr 166 is a typical feldspathic lunar meteorite. It is indistinguishable from the Dhofar 026 clan in composition, but Shişr 166 has a distinctly different in texture. None of the 4 Shişr lunar meteorites is paired with another.
Meteoritical Bulletin Database
Bouvier A., Wadhwa M., Korotev R. L., and Hartmann W. K. (2011) U-Pb chronology of two lunar impact melt breccias. 74th Annual Meeting of the Meteoritical Society, abstract no. 5185.
Korotev R. L. (2012) Lunar meteorites from Oman. Meteoritics & Planetary Science 47, 1365-1402.
Korotev R. L. (2017) Update (2012–2017) on lunar meteorites from Oman. Meteoritics & Planetary Science 52, 1251-1256.
Korotev R. L., Irving A. J., and Bunch T. E. (2012) Keeping Up With the Lunar Meteorites – 2012. 43rd Lunar and Planetary Science Conference, abstract no. 1152.
Mészáros M., Leya I., and Hofmann B. A. (2016) Noble gases in the two lunar meteorites AaU 012 and Shişr 166. 79th Annual Meeting of the Meteoritical Society, abstract no. 6129.
Mészáros M., Leya I., and Hofmann B. A. (2017) Cosmic-ray exposure histories of the lunar meteorites AaU 012 and Shişr 166. Meteoritics & Planetary Science 82, 2040–2050.