Northwest Africa 12821 (NWA 12821)

(Northwest Africa)

Purchased: 2019

Classification: Enstatite chondrite (EL3)

History: Purchased by Habib Naji, Morocco, 6 Jan 2019, from a nomad who reportedly found the meteorite.

Physical characteristics: Single stone with fusion crust, outlines of small chondrules are visible on the surface. Saw-cut surface reveals abundant bright metal/sulfide grains making up 15-20% of this meteorite. Numerous small chondrules are present in a dark gray matrix.

Petrography: (C. Agee, UNM) Microprobe examination of a polished mount shows many distinct, well formed chondrules with dominant enstatite and lesser forsterite, apparent mean diameter 375±200 μm (n=18). Some chondrules are mantled with metal or contain many fine-grained metal/sulfide inclusions. Very fine-grained metal is dispersed throughout the matrix, numerous larger metal grains up to 500 μm are ubiquitous. No feldspar was detected.

Geochemistry: : (C. Agee, UNM) Forsterite Fa_0.3±0.2, n=20; enstatite Fs_1.6±1.8Wo_0.7±0.9, Fe/Mn=9±3 n=12; oldhamite Ca=52.9, Mn=1.12, S=43.2 (all wt%), n=3; Cr-bearing troilite Cr=2.7±1. (wt%), n=5; kamacite Ni=6.6±0.2, Si=1.32±0.02, n=10. Oxygen isotopes (K. Ziegler, UNM): 8 acid-washed fragments analyzed by laser fluorination gave, respectively δ¹⁸O= 5.892, 5.846, 6.049, 6.023, 6.068, 6.091, 6.402, 6.081; δ¹⁷O= 3.045, 3.119, 3.359, 3.212, 3.216, 3.168, 3.367, 3.254; Δ¹⁷O= -0.065, 0.032, 0.166, 0.032, 0.012, -0.048, -0.013, 0.043 (linearized, all per mil, TFL slope=0.528).

Classification: Enstatite chondrite (EL3), type 3 based on presence of numerous, well-formed type I chondrules. EL based on Si content of kamacite.

Specimens: 20.5 g including a probe mount on deposit at UNM, Habib Naji holds the main mass.