Diogenite
Norite
Purchased May 2011
no coordinates recorded
A single stone weighing 223 g was purchased by G. Fujihara from a Moroccan dealer. A sample was submitted for analysis and classification to the University of Washington at Seattle (A. Irving). While it was initially considered that NWA 6928 was likely an unusual basaltic eucrite, it was quickly determined that it was actually a rare noritic diogenite containing pyroxene in the form of orthopyroxene rather than pigeonite, and consisting of >10 vol% plagioclase. New terminology has been proposed in a revision to the diogenite classification scheme utilizing an IUGS-based system (Beck and McSween, 2010; Wittke et al., 2011).
Northwest Africa 6928 has a relatively coarse-grained, cumulate texture, which exhibits localized shock features including undulose extinction and cataclasis. It is composed of 80 vol% orthopyroxene and 19 vol% interstitial anorthitic plagioclase, along with accessory Ti–Al-bearing chromite, troilite, and merrillite. An oxygen-isotopic analysis will be completed at Okayama University.
To date only two other noritic diogenites are known. For more details on the formation of diogenites visit the Johnstown page. The photo of NWA 6928 shown above is a 3.03 g slice expertly prepared by Montana Meteorite Laboratory. The top photo shown below is the reverse side of the 3.03 g slice, while the bottom photo shows the main mass prior to cutting.
