Northwest Africa 10922 (NWA 10922)

(Northwest Africa)

Purchased: 2013

Classification: Martian meteorite (basaltic breccia)

History: Purchased by Jay Piatek from Adam Aaronson in Morocco, 2013.

Physical characteristics: Single stone. The stone appears to have been sitting in the desert soil only half exposed for a relatively long time, as one side appeared smoothed and shiny, with a sand-blasted, black exterior, while the other side was covered with light-yellow caliche. Upon removal of the caliche with diluted glacial acetic acid, a preserved, brown colored, glassy, flow-lined, fusion crust was revealed. Saw cut shows a breccia with numerous dark and light colored fragmental crystals and polycrystalline lithologies, scattered spherules and spherical objects. An unusual trapezium-shaped object (~ 5mm) was observed, containing dark red concentric layers or zones, with a spherule at its center. Groundmass is dark gray, fine-grained, with scattered opaques throughout.

Petrography: (C. Agee, UNM) Microprobe examination of the polished deposit sample shows a polymict breccia with fragmental feldspar and pyroxene crystals up to 5 mm, iron-oxide-rich spherules, silicate-rich spherules, all set in a very fine-grained groundmass composed of feldspar, pyroxene, oxides, phosphates, zircon, baddeleyite, and sulfides. The trapezium-shaped object described above consisted of distinct zones or layers of very fine-grained mixture of feldspars, pyroxenes and opaques. The sphere at the center of the trapezium shaped object contained euhedral olivine grains set in a quench-melt groundmass.

Geochemistry: (C. Agee, M. Spilde, M. Habermann UNM) plagioclase Ab_54.8±5.7An_43.1±6.3Or_2.1±0.6, n=9; albitic feldspar Ab_84.0An_2.7Or_13.3, n=1; potassium feldspar Ab_24.5±2.6An_3.7±1.5Or_71.7±4.1, n=2; low-Ca pyroxene Fs_31.2±7.7Wo_3.7±2.1, Fe/Mn=35±3, n=17; augite Fs_24.1±8.3Wo_38.6±7.5, Fe/Mn=32±5, n=2; olivine Fa_34.3±0.5, Fe/Mn=38±2, NiO=0.53±0.05 (wt%), n=5. Oxygen isotopes (K. Ziegler, UNM) acid-washed material analyzed in 4 replicates by laser fluorination gave, respectively δ¹⁸O= 6.192, 5.992, 5.746, 5.960; δ¹⁷O= 3.826, 3.750, 3.588, 3.714; Δ¹⁷O= 0.557, 0.586, 0.554, 0.567 (linearized, all per mil).

Classification: Martian (basaltic breccia). Paired with NWA 7034. This specimen is the only known NWA 7034 pairing with documented glassy fusion crust.

Specimens: 22 g on deposit at UNM, Jay Piatek holds the main mass.