A fragmented stone weighing 252 g was collected in Algeria from a similar location as NWA 2968. The fragments were subsequently purchased in Er-Rachidia, Morocco by collector F. Kuntz. A sample of these fragments was analyzed at the University of Washington at Seattle (A. Irving and S. Kuehner) and NWA 3329 was determined to be a diogenite composed primarily of coarse-grained, dark brown orthopyroxene, together with interstitial plagioclase, silica, phosphate, FeNi-metal, and FeS.
The NWA 3329 fragments were subsequently studied by Barrat et al. (2010). Interestingly, some fragments from the batch were found to be identical to the NWA 2968, while petrographic evidence indicated that both lithologies were collected from the same location. Notably, other fragments that were found consist of both lithologies together, diogenite and dunite, which are each identical to their respective type samples. Trace element studies were conducted on both lithologies and they were found to be consistent with pairing. Moreover, their O-isotopic values are indistinguishable. The investigators interpret the evidence to indicate that both diogenite and dunite lithologies are fragments from a common fall, possibly as components of a mesosiderite.
A comparison of reflectance spectra of seven near-Earth asteroids to those of HED-group meteorites by Burbine et al. (2009) revealed that all of the pyroxene mineralogies were consistent with eucrites and howardites but not to diogenites. Therefore, they suggest that there are no km-sized or larger objects composed strictly of diogenite material, but instead, diogenites may exist as mixtures of all the lithologies of the HED asteroid. Beck et al. (2012) identified the first olivine-rich melt material in howardites that constitute the PCA 02009 pairing group. This olivine-rich material was likely derived from harzburgitic and dunitic lithologies exposed on the surface of Vesta.
To see an alternative classification system for the diogenites and dunites based on mineralogical and petrographical features, proposed by Beck and McSween (2010) and modified by Wittke et al. (2011), click here. The photo shown above is a 0.52g fragment of NWA 3329.
