Northwest Africa 12273 (NWA 12273)

(Northwest Africa)

Purchased: 2018

Classification: Ungrouped chondrite

History: Purchased by Jay Piatek from a Moroccan meteorite dealer on October 25, 2018.

Physical characteristics: Dense, single individual. Fusion crust absent; abundant bright metal; scattered small chondrules are visible.

Petrography: (C. Agee, UNM) This meteorite consists of approximately 75% metal in the form of kamacite (~90%) and taenite (~10%) grains, diameters ranging from 50-500 μm. Minor troilite was observed throughout. Silicates occur primarily in the form of chondrules, most are porphyritic, diameters in the range 100-500 μm, making up approximately 20% of this meteorite.

Geochemistry: (C. Agee) Olivine Fa_26.2±3.3, Fe/Mn=55±5, n=29; low-Ca pyroxene Fs_15.3±1.8Wo_0.7.±0.2, Fe/Mn=23±2, n=11. Oxygen isotopes (K. Ziegler, UNM): 3 acid-washed fragments analyzed by laser fluorination gave δ¹⁸O= 5.258, 5.613, 7.249; δ¹⁷O= 3.939, 3.971, 4.786; Δ¹⁷O= 1.163, 1.007, 0.959 (linearized, all per mil, TFL slope=0.528).

Classification: Ungrouped chondrite. This is a metal-rich chondrite with oxygen isotopes that overlap with LL-chondrites. The olivine Fa content is consistent with L3, however the low-Ca pyroxene Fs is consistent with H4. The high metal content is inconsistent with ordinary chondrite. Texturally, this meteorite resembles a CB-b, however the oxygen isotopes and Fa and Fs are unlike CB chondrites.

Specimens: 23.2 g including a probe mount on deposit at UNM, Jay Piatek holds the main mass of 240 g.