Lunar Meteorite: Northwest Africa 12592 & 12593

from The Meteoritical Bulletin, No. 108

Northwest Africa 12592 (NWA 12592)

Algeria
Purchased: 2017
Mass: 1420 g (1 piece)

Lunar (fragmental breccia)

History: A single weathered stone lacking a fusion crust was found by nomads in Algeria and purchased by Dustin Dickens in Nouakchott, Mauritania in 2017 from an anonymous meteorite dealer.

Physical characteristics: Dark grey sandblasted exterior, with many irregular shaped fragments set in a fine grained vesiculated groundmass. No fusion crust.

Petrography: (T. S. Hayden, M. Anand, OU) The meteorite is a clast-rich fragmental breccia containing numerous mineral and lithic fragments embedded in a fine-grained vesiculated (regolith) matrix. The lithic clast population consists primarily of basaltic clasts, dominated by Ca-rich pyroxene and plagioclase, with minor olivine components. The size range of the lithic clasts is 0.19-1.9 mm. Mineral clasts are mainly pyroxene, olivine, plagioclase, chromite, troilite and Fe-Ni phases. Some impact melt textures present also.

Mineral composition and Geochemistry: (T. S. Hayden, M. Anand, OU) Feldspar (An_95.2±0.7Ab_4.7±0.7, N = 31), Pigeonite (Fs_43±3.3Wo_9.5±4.4, Fe/Mn=65.5±3.3, N=45), Augite (Fs_25±4.8Wo_35.7±6.1, Fe/Mn=59.5±5.6, N=54), Clinoferrosilite (Fs_48.6Wo₅, Fe/Mn = 67.4, N=1), Clinoenstatite (Fs_44.5±4.3Wo_4.4, Fe/Mn = 64.7±3.9, N=11), Olivine (Fa_47.6±16, Fe/Mn=104.5±10.8, N=33). O isotopes (measured at OU): Repetition 1: δ¹⁷O = 3.266‰, δ¹⁸O = 6.333‰, Δ¹⁷O=-0.052 (linearized using a slope of 0.5247), Repetition 2: δ¹⁷O = 3.217‰, δ¹⁸O = 6.174‰, Δ¹⁷O=-0.018‰ (linearized using a slope of 0.5247. Mean: δ¹⁷O = 3.242 ± 0.035‰ (1-sigma), δ¹⁸O = 6.254 ± 0.112‰ (1-sigma), Δ¹⁷O=-0.035±0.024 (1 sigma).

Classification: Lunar fragmental regolith breccia.

Specimens: Specimen: 20 g specimen held at OU. Dustin Dickens holds the main mass.

from The Meteoritical Bulletin, No. 108

Northwest Africa 12593 (NWA 12593)

Mali
Purchased: 2017
Mass: 332.8 g (1 piece)

Lunar (fragmental breccia)

History: A single weathered stone lacking fusion crust found in Mali by nomads. Purchased by Dustin Dickens in Nouakchott, Mauritania, in 2017 from an anonymous meteorite dealer.

Physical characteristics: Dark, sand-blasted exterior, with many irregular shaped fragments set in a fine-grained dark groundmass. No fusion crust.

Petrography: (T. S. Hayden, M. Anand, OU) The meteorite is clast-rich fragmental breccia containing numerous mineral fragments and lithic clasts embedded in a fine-grained, vesiculated (regolith) matrix. The lithic clast population consists of basaltic clasts, granulite clasts and crystalline impact-melt breccias of olivine norite compositions. Size range of the clasts is 0.56-2.56 mm, and the main minerals are pyroxene, feldspar, olivine, silica, chromite, ilmenite, zircon and Ca phosphates (merrillite and apatite).

Mineral composition and Geochemistry: (T. S. Hayden, M. Anand, OU) Feldspar (An_93.8±2.7, Ab_5.9±2.5, n=39), pigeonite (Fs_30.5±9.1Wo_13.1±3.4, FeO/MnO = 59.3±6.6, n=59), augite (Fs_23.1±6.1Wo_30.9±4.3, FeO/MnO = 54.2±4.4, n=18), olivine (Fa_38.2±11.7, FeO/MnO = 103.2±7.1, n= 40). O isotopes (measured at OU): Repetition 1: δ¹⁷O = 3.328‰, δ¹⁸O = 6.361‰, Δ¹⁷O=-0.005‰ (linearized using a slope of 0.5247 (of Miller, M. F. (2002) GCA 66(11)), Repetition 2: δ¹⁷O = 3.203‰, δ¹⁸O = 6.106‰, Δ¹⁷O=-0.004‰ (linearized using a slope of 0.5247. Mean: δ¹⁷O = 3.266 ± 0.088‰ (1-sigma), δ¹⁸O = 6.234 ± 0.180‰ (1-sigma), Δ¹⁷O=0.000±0.006‰ (1-sigma).

Classification: Lunar fragmental regolith breccia.

Specimens: Specimen: 24 g type specimen held at OU. Dustin Dickens holds the main mass.

Randy Says…

I have not studied Northwest Africa 12592 and 12593  I presume that they are paired with each other because of the similar descriptions. Both might also be pairs of the NWA 8046 clan.

More Information

Meteoritical Bulletin Database

NWA 12592 & 12593

References

Crow C. A., Economos R., Lehman K., Pomeroy S., Erickson T., Brounce M., and Boyce J. (2022) Chronology of accessory phases in lunar meteorite Northwest Africa 12593. 53rd Lunar and Planetary Science Conference, abstract no. 2524.

Crow C. A., Erickson T. M., Economos R., and Lehman Franco K. (2023) An ~3.5 Ga impact recorded by cubic baddeleyite in lunar meteorite Northwest Africa 12593. 85th Annual Meeting of the Meteoritical Society, abstract no. 6270.

Hayden T. S., Barrett T. J., Zhao X., Degli-Alessandrini G., Anand M., Franchi I. A. (2021) Chlorine and hydrogen in brecciated lunar meteorites: Implications for lunar volatile history. 52nd Lunar and Planetary Science Conference, abstract no. 1550.

Lehman Franco K. M., Economos R., Crow C. A., Erickson T., Pomeroy S., and Summerlin E. (2024) Modeling the ²³⁸U/²⁰⁴Pb μ and initial Pb of lunar meteorite Northwest Africa 12593. 55th Lunar and Planetary Science Conference, abstract no. 2786.