Northwest Africa 8545 (NWA 8545)

(Northwest Africa)

Purchased: 2013

Classification: Ungrouped achondrite

History: Purchased by Brahim Tahiri from a Moroccan hunter and sent to his partner Sean Tutorow for classification, April, 2013.

Physical characteristics: Single stone. Exterior shows remnants of black fusion crust, saw cut reveals light orange-brown crystalline texture with scattered dark grains ~1 mm, moderately friable.

Petrography: (C. Agee, UNM) Microprobe examination of a polished mount shows approximately 70% pyroxene and ~30% plagioclase. Pyroxenes all show exsolution lamellae, grains are 500-2000 μm, and have a striking appearance in that the grain boundaries are all very irregular with ~50 μm embayments and protrusions. Plagioclase is interstitial to pyroxene and poikioblastic with silica inclusions, some grains up to 1000 μm. Accessory troilite and Cr-Ti oxides.

Geochemistry: (C. Agee and N. Muttik, UNM) Pigeonite Fs_62.4±1.9Wo_7.6±2.1, Fe/Mn=69±2, n=9; augite Fs_39.9±5.4Wo_34.0±6.3, Fe/Mn=67±5, n=8; olivine Fa_84.2, Fe/Mn=89, n=1; plagioclase An_85.3±2.6Ab_14.2±2.5Or_0.4±0.1, n=10. Oxygen isotopes (K. Ziegler, UNM) Oxygen isotope values of 3 acid-washed aliquots of bulk sample, 1.3, 1.3, 2.1 mg, gave δ¹⁷O = 0.004, 0.120, 0.013, δ¹⁸O = 2.966, 3.159, 2.297, Δ¹⁷O = -1.562, -1.548, -1.532 (linearized, all permil).

Classification: Achondrite (ungrouped), probably paired with NWA 011 and NWA 2976.

Specimens: 11.7 g including a probe mount on deposit at UNM, Sean Tutorow holds the main mass.