Several fusion-crusted stones having a combined weight of 380 g were found near Foum Zguid, Morocco and purchased by R. Chaoui. These were subsequently acquired by a number of meteorite dealers, including material purchased by G. Fujihara from R. Chaoui's brother. Sample analyses were conducted at the University of Washington at Seattle (A. Irving and S. Kuehner), Arizona State University (L. Garvie), and the University of New Mexico (oxygen isotope analysis; K. Ziegler). The meteorite was classified as an ungrouped carbonaceous chondrite.
The silicates identified in NWA 8781 include olivine, orthopyroxene, and diopside, along with the opaque minerals kamacite and troilite. The fine-grained matrix material constitutes ~50 vol%, and no phyllosilicates were observed. Chondrules are very small (210 [±60] µm) compared to those in CV and CK chondrites. The apparent absence of CAIs is also inconsistent with CV as well as CO chondrites, and the lack of magnetite is inconsistent with CK chondrites. In addition, the O-isotopic values for NWA 8781 plot in a space distinct from other known carbonaceous chondrite groups, but very close to that for the C3-ungrouped NWA 12416 (see diagrams below).
Diagram from MetBull 107
Diagram credit: Greenwood et al., GCA, vol. 277, p. 381 (2020, open access link)
'Linking asteroids and meteorites to the primordial planetesimal population'
Northwest Africa 8781 has experienced a low degree of terrestrial weathering, and it has features indicative of very weak shock (S2). The specimen of NWA 8781 shown above is a 0.77 partial slice photographed with a cm-scale cube, courtesy of Gary Fujihara.
Read the Micro Visions article for September 2020 about NWA 8781 in Meteorite Times Magazine, written by John Kashuba and including his always excellent thin section photomicrographs.