from The Meteoritical Bulletin, No. 108
Saguia el Hamra, Western Sahara
Lunar meteorite (gabbro)
History: Two large stones (2338 g, 1754 g) and several smaller stones were found together. One stone (177 g) was purchased by Darryl Pitt in November 2018. The 1754 g stone was purchased by Aziz Habibi in January 2019, and subsequently acquired by Darryl Pitt, who independently purchased three additional stones from several Mauritanian dealers in March 2019.
Physical characteristics: All stones lack fusion crust. Fresh interiors have a mottled dark gray appearance with a relatively coarse grained, equigranular texture.
Petrography: (A. Irving, UWS and P. Carpenter, WUSL) Coarse grained, with a gabbroic texture (mean grainsize 1.5 mm). Composed of patchily zoned clinopyroxene, maskelynite, and olivine, with accessory ilmenite, troilite, tranquillityite, Th-free monazite and rare kamacite. Minor secondary calcite and hyalophane were observed on some grain boundaries.
Geochemistry: Olivine (Fa66.6-84.2, FeO/MnO = 92-102, N = 3), pigeonite cores (Fs30.1-31.6Wo13.4-10.4, FeO/MnO = 53, N = 2), pigeonite rim (Fs44.4Wo12.5, FeO/MnO = 59), subcalcic augite rim (Fs46.9Wo32.8, FeO/MnO = 71), maskelynite (An85.1-89.1Or0.8-0.3, N = 2).
Classification: Lunar (mare gabbro).
Specimens: 46.9 g including one polished thin section and one polished endcut at UWB; remainder with DPitt.
from The Meteoritical Bulletin, No. 108
Lunar meteorite (basalt)
History: Purchased by Jay Piatek in 2021 from a meteorite dealer in Mauritania. Found by a meteorite hunter win the region of Alaug Alkabli, Western Sahara, about 75 km from Almahbas.
Physical characteristics: Single stone, irregular pitted surface with about 20% preserved smooth black fusion crust, the rest of the exterior is sand-blasted from desert weathering. Some orange caliche coating is also present. A freshly exposed surface from the deposit sample chip reveals a medium to fine-grained texture of light and dark colored mineral phases. Ubiquitous shiny transparent-colorless maskelynite glass is macroscopically visible, as are scattered shiny black shock melt veinlets. Unbrecciated.
Petrography: (C. Agee, UNM) Backscattered electron images shown igneous-zoned olivines and pyroxenes most in the size range of 500-1000 μm. Maskelynite makes up approximately 25% of the modal mineralogy, ilmenite ~3%, minor troilite and silica observed.
Geochemistry: (A. Ross and C. Agee, UNM) Olivine Fa56.1±11.2, Fe/Mn=104±8, n=10; pigeonite Fs36.3±4.9Wo13.6±3.4, Fe/Mn=59±5, n=19; augite Fs24.7±3.3Wo32.7±0.8, Fe/Mn=53±5, n=5; subcalcic ferroaugite Fs53.1±5.7Wo22.1±4.6, Fe/Mn=73±3, n=6, maskelynite An88.8±2.8Ab10.7±2.8, n=12. Displayed in the pyroxene quadrilateral, augite and pigeonite show Fe-enrichment trends that converge into subcalcic ferroaugite.
Classification: Lunar (mare basalt)
Specimens: 37.5 g including a probe mount on deposit at UNM, Jay Piatek holds the main mass.
I have not studied Swayyah 001 and 004. Preliminary data show concentrations of incompatible elements in Swayyah 001 to be very low. I assume that the stones are paired because basalt and gabbros are uncommon (<10%) among lunar meteorites and the stones were found 5 km apart. The fact that Dr. Irving calls Swayyah 001 a gabbro and Dr. Agee calls Swayyah 004 a basalt is largely irrelevant. By definition, the mineral grain size is <1 mm in a basalt and >1 mm in a gabbro; otherwise they are the same. Many “mare basalts” of the Apollo collection are, technically, gabbros. Lunar meteorites (launch pairs) Asuka 881757 and Miller Range 05035 are by definition, gabbros, but the latter is as described as a basalt in the classification.
Meteoritical Bulletin Database
Shi E., Carpenter P. K., Jolliff B. L., Chen J., Wang A., Tepper J. H., Irving A. J., Burney D. C., Neal C. R. (2020) Mineralogical and petrological analysis of lunar mare gabbro meteorite Swayyah 001 (abstract #2923). 50th Lunar and Planetary Science Conference.