from The Meteoritical Bulletin, No. 110
Northwest Africa 13788 (NWA 13788)
Classification: Lunar meteorite (melt breccia)
History: Purchased in 2021 by Matthew and Travis Stream from a meteorite dealer in Algeria.
Physical characteristics: Specimen contains a dark-brown fusion crust. An interior slice reveals light and dark clasts within a darker matrix.
Petrography: (D. Sheikh, FSU) Sample is an impact melt breccia composed of angular to sub-rounded mineral and lithic clasts (<4 mm) set in a predominantly vitreous matrix composed of brown, flow-banded, vesicular, partly devitrified glass and fine-grained crystalline impact melt. Lithic clasts consist primarily of anorthitic plagioclase (some partially converted to maskelynite) with smaller quantities of olivine, pigeonite, low-Ca pyroxene, sub-calcic augite, and Si-Na-Ca-Mg-rich glass; a variety of lithic clasts were observed to display poikilitic, granulitic, dendritic, porphyritic, or subophitic textures in thin section. Accessory phases present include kamacite, troilite, chromite (some containing Ti), and ilmenite.
Geochemistry: Olivine (Fa32.8±5.9, range Fa18.3-43.1, Fe/Mn=74±11, n=22), Low-Ca pyroxene (Fs34.5±13.1 Wo2.9±1.5, range Fs19.2-42.2 Wo1.5-4.4, Fe/Mn=46±13, n=3), Pigeonite (Fs34.4±9.7 Wo15.0±5.3, range Fs19.5-48.0 Wo6.4-23.7, Fe/Mn=47±6, n=11), Sub-calcic augite (Fs28.6±9.2 Wo31.8±4.5, range Fs14.4-39.2 Wo26.7-39.1, Fe/Mn=44, n=6), Anorthite (An96.1±0.7, range An94.5-97.8, n=42).
Classification: Lunar (melt breccia).
Specimens: 20.3 g at UCLA; main mass with Matthew and Travis Stream.
I have not studied NWA 13788. From the description and photos, it might be another NWA 8673 pair. Note that the official mass is 2600 g in 3 pieces. As of March, 2020 there are a several what appear to be uncut stones in the tens of grams mass range being sold as NWA 13788 on the internet. Maybe they are unofficial pairs, but I don’t know how we know that.
Meteoritical Bulletin Database