Northwest Africa 14518 (NWA 14518)

(Northwest Africa)

Purchased: 2021

Classification: Mesosiderite (group A3)

History: Purchased from a Moroccan meteorite dealer in 2021.

Physical characteristics: Single object with irregular, dark gray-brown exterior. Saw cut reveals numerous irregular metal domains >1 mm, but also abundant fine-grained metal, distributed uniformly throughout a silicate groundmass.

Petrography: (A. Ross and C. Agee, UNM) Microprobe examination of a polished mount shows pyroxene making up approximately 75% of the silicate portion of this meteorite, ~25% plagioclase, with ~5% minor phases silica, ilmenite, merrillite, chromite, rutile, and troilite. Some pyroxene grains have exsolution lamellae. Plagioclase is often poikilitically enclosed in larger pyroxene grains; no was olivine detected. Metal makes up approximately 35% of this meteorite and is primarily segregated into irregular ameboid domains >1 mm, although there are scattered smaller (~10 ?m) grains throughout the silicate domains. Both kamacite and taenite are present. No brecciation observed.

Geochemistry: (A. Ross, UNM) Low-Ca pyroxene Fs_31.5±1.3Wo_4.3±0.51, Fe/Mn=26±1, n=4; high-Ca pyroxene Fs_17.7±0.9Wo_37.4±1.6, Fe/Mn=23±1, n=3; plagioclase An_88.4±2.0Ab_11.0±1.9Or_0.6±0.2, n=6; kamacite Fe=93.7±0.2, Ni=6.5±0.2, Co=0.49±0.02 (wt%), n=3; taenite Fe=49.2±2.5, Ni=50.4±2.2, Co=0.07±0.02 (wt%), n=3

Classification: Mesosiderite-A3. Relatively high abundance of plagioclase and silica consistent with group A. Segregated metal, presence of some texturally and chemically equilibrated silicates, and absence of significant brecciation consistent with type 3.

Specimens: 47.1 g on deposit at UNM, Craig Zlimen and Brett Joseph Cohen hold the main mass.