Morocco
Find: 2006
Achondrite (aubrite)
History and physical characteristics: Hundreds of platey fragments, the largest weighing 33.1 g, were found in the Western Sahara region of Morocco and purchased by A. Aaronson in 2007. The total known weight is 268g. Fragments tend to break along the preferred orientation plane of constituent enstatite grains. Most of the dark brown pieces are moderately to heavily weathered, a few show small, fresh metal nuggets.
Petrography (T. Bunch and J. Wittke, NAU): composed mostly of fine-to medium-grained (0.3 to 1.2 mm), euhedral to subhedral cumulate enstatite together with interstitial metal, schreibersite, graphite, a silica phase present as round inclusions in FeS, FeS, daubreelite, brezinaite and very fine-grained intercumulus plagioclase. Much of the metal is oxidized. The stone is unbrecciated with a low shock level.
Mineral chemistry: Enstatite is essentially Fe-free (En99.6Fs0.1Wo0.3). Kamacite is Si-enriched (Si = 4.5 to 5.6 wt. %) and FeS contains 2.6 wt. % Ti. The rare mineral brezinaite contains S, 45.2 wt. %; Cr, 36.9 to 46.6 wt. %; Fe, 18.7 to 9.0 wt. % and 1.1 wt. % Mn.
Classification: Achondrite (aubrite).
Type specimen: A total of 20.6 g is on deposit at NAU. Mr. A. Aaronson is the main mass holder.
Morocco
Find: 2006
Achondrite (aubrite)
History and physical characteristics: Sixty-one pieces with a total weight of 906 g were purchased in Tagounite, Morocco in May 2007. Most of the stones are medium to dark brown with some remnant fusion crust.
Petrography (T. Bunch and J. Wittke, NAU): A brecciated cumulate rock with clasts as large as two cm. The intact lithology is dominated by subhedral to anhedral polysynthetically twinned enstatite with fine-grained intercumulus intergrowths of feldspathic glasses and a silica phase. Other minerals include graphite, FeS, daubreelite, schreibersite, niningerite, perryite as exsolution lamellae in Si-bearing kamacite and Zn-bearing brezinaite. Large clasts show a multitude of sub-parallel, closely spaced compression fractures. Shock level is S3 and the weathering grade is W5 for small pieces (< 3 cm) and W3 for the interiors of larger specimens.
Mineral compositions: Enstatite is essentially Fe-free (Fs0.1Wo0.3), kamacite Si content is 3.1 to 3.6 wt. % and perryite is (in wt. %): Si, 12.4; Fe, 4.5; Ni, 77.5 and P, 3.8. Zincian brezinaite is (in wt. %): Cr, 43.2; S, 44.1; Fe, 6.3; Mn, 1.2; Zn, 5.1.
Classification: Achondrite (aubrite), possibly paired with NWA 4799.
Type specimen: A total of 22.3 g are on deposit at NAU. Mr. A. Aaronson holds the main mass.
