A mass of 27 kg was found by a rabbit trapper 5 miles west of Corkwood Tank in Queensland, Australia. Naryilco was analyzed and classified at the Institut für Planetologie, University of Münster, Germany. The meteorite is a breccia composed of angular, cm-sized light and dark lithic clasts with shock veins, the result of prolonged impacts on its parent body. Subsequent impacts generated enough heat to cause minor melting along grain boundaries, fusing the different clasts together.
Naryilco is a transitional chondrite having characteristics of both L and LL chondrite groups; in particular, the Fa content of 26.4 mol% is within the upper range defined by other L/LL chondrite members. It has a Fs content of 22.1 mol%, but no Fs range has yet been determined for this transitional group. During their studies of chromite-encapsulated silicates in fossil meteorites, Alwmark and Schmitz (2009) determined the Fa and Fs values for Naryilco to be 24.3 mol% and 20.2 mol%, respectively, which places it within the L chondrite range.
ORDINARY CHONDRITE COMPOSITIONS
*M. Ivanova (Chug Chug 019); Yamaguchi et al., 2019
It was demonstrated by Szurgot (2016) that the mean atomic weight (Amean) of meteorites can be used to resolve the OC groups, including the intermediate groups L/LL and H/L. Amean values can also be predicted through various equations based on other parameters such as atomic Fe/Si ratio, grain density, and magnetic susceptibility, and these Amean values all consistently resolve these groups into the ordered sequence LL < L/LL < L < H/L < H. Furthermore, it was demonstrated that Amean values are lower for unequilibrated type 3 samples than for equilibrated samples within each OC group due to the presence of water; Amean values for petrologic types 46 are indistinguishable within each group.
Diagram credit: M. Szurgot, 47th LPSC, #2180 (2016) Amean based on chemical composition (Eq. 1), Fe/Si atomic ratio (Eq. 2), and grain density (Eq. 3)
Examples of other L/LL6 group members include the Acfer meteorites 041, 149, and 315, the HaH meteorites 046 and 074, Holbrook, and Sahara 97012. The Naryilco specimen shown above is a 1.44 g partial slice. A superb large slab can be seen on display at the Smithsonian Institution, Washington D.C.