A single weathered (W3) meteorite weighing 1,276 g was found in Algeria and sold to a meteorite dealer in Erfoud, Morocco. Analysis and classification of the stone was conducted at Northern Arizona University (T. Bunch and J. Wittke), and it was determined that NWA 5206 is a very weakly shocked (S2), terrestrially weathered (W3), highly unequilibrated LL3.05 (or possibly lower) chondrite.
Chondrules of both type-I and type-II compositions are present in a ratio of 3:1, respectively. Chondrule textures span a broad range; porphyritic types predominate, while the remainder comprises granular, radial, cryptocrystalline, barred, and a number of unique types, some with thick mantles. In addition to the primitive compositional heterogeneity of this chondrite, other petrographic and chemical characteristics, such as the alkali-poor glassy chondrule mesostasis and the Cr distribution in ferroan olivine, has led investigators to conclude that NWA 5206 is highly unequilibrated with a subtype <3.1. A more extensive review of the most recent techniques used to discriminate among the lowest petrologic types can be found on the NWA 1756 page.
Utilizing AlMg chronometry for a broad sampling of unequilibrated ordinary chondrites, Pape et al. (2019) ascertained that five type-II chondrules from NWA 5206 provide 26Al26Mg isochron ages of ~1.97 to ~2.64 m.y. after formation of CAIs (see diagram below). The total age range for the entire sample set is ~1.76 to ~2.92 m.y. after CAIs, attesting to chondrule formation occurring over an interval of ~1.2 m.y., or ~1.5 m.y. when including the oldest known chondrules.
Diagram credit: Pape et al., GCA, vol. 244, p. 429 (2019)
'Time and duration of chondrule formation: Constraints from 26Al-26Mg ages of individual chondrules'
Prior to this period of chondrule formation, the parent body of IVA irons had already accreted and undergone differentiation in the same nebular reservoir as the LL chondrite parent body. This was demonstrated by Anand et al. (2012) using a coupled ε54Cr vs. Δ17O diagram (see diagram below).
Chromium vs. Oxygen Isotope Diagram
Diagram credit: Anand et al., 84th MetSoc, #6154 (2021)
Very few ordinary chondrites have been classified as petrologic subtype 3.05 or lower, and NWA 5206 is the only LL chondrite designated as such. A comprehensive pictorial review of NWA 5206 can be found on the Meteorites Australia page showing examples of the many chondrule types and exotic components such as metallic chondrules armored with troilite, xenolithic chondrule fields, and dark inclusions. The specimen of NWA 5206 shown above is a 7.47 g partial slice. The photo below shows a view of the main mass, courtesy of M. Cimala.