NORTHWEST AFRICA 974


E6, ungrouped
(revised in 2008 from EH6 grouping in MetBull 86)
standby for nwa 974 photo
Found April 2001
no coordinates recorded

A single highly-weathered stone weighing 2,250 g was found by villagers near Remlia, Morocco, in April 2001. Northwest Africa 974 is composed primarily of enstatite and kamacite, along with minor plagioclase, oldahmite, daubreelite, alabandite, schreibersite, troilite, graphite and silica. It is moderately shocked to stage S4.

Despite its high content of kamacite, long considered to be diagnostic of an EH classification, other compositional characteristics are more consistent with an EL classification. Indeed, it has been demonstrated by Macke et al. (2009) that these two groups do not actually differ in their iron content, and that they are indistinguishable in density, porosity, and magnetic susceptibility as well; however, differences in siderophile, chalcophile, and other mineralogical abundances can be employed to distinguish the two groups. For example, the presence of alabandite rather than niningerite in NWA 974 is typically diagnostic of the EL group, as is the relatively high content of anorthite present. The classifying investigator (A. Jambon, Université Pierre & Marie Curie) believes that these features represent anomalous characteristics attributable to the high metamorphism which the stone has experienced, and he has suggested a classification of EH6 as most appropriate for this stone. Further studies should help resolve the ambiguity in the classification of this enstatite chondrite.

On May 8, 2008 the classification of NWA 974 was revised by the Nomenclature Committee of the Meteoritical Society to reflect a recommendation of E6 chondrite, pending further analyses. The specimen of NWA 974 shown above is a 2.89 g partial slice.