Tin-Essako 001 (TE 001)        18.280242, 2.094914

Gao, Mali

Find: 2020

Classification: Ungrouped achondrite

History: Purchased by Jay Piatek in 2021 from meteorite dealers Hassan Ounir and Ali Benamar. Found in 2020 by a nomad in Mali approximately 120 km east of the town of Kidal.

Physical characteristics: Oriented single stone, irregular surface, dark colored exterior patina with some reddish-brown oxidation patches. Saw cuts reveal a stony-iron appearing interior with a heterogenous distribution of metal and silicate grains and domains. Cut metal surfaces appear fresh with only minor oxidation. Silicates are very dark brown in color.

Petrography: (C. Agee, M. Spilde, UNM) This meteorite consists of approximately 50% silicates and 50% metal. The dominant silicate mineral is olivine; metal consists of kamacite. Backscatter electron imaging gives the approximate modal silicate abundances: 85-90% olivine, 10% plagioclase, and minor chromite, and quench melt pockets. Small (<100 μm) carbon rich phases (possibly graphite) at olivine-metal grain boundaries and as inclusions in metal were found. No pyroxenes, sulfides, or diamonds were detected in the microprobe mount.

Geochemistry: (C. Agee, M. Spilde, UNM) Olivine Fa_25.0±0.1, Fe/Mn=51±2, Cr₂O₃=0.27±0.02 wt%, CaO=0.24±0.01 wt%, n=8; plagioclase An_54.0±1.5Or_0.2±0.1Ab_45.8±1.5, n=7; melt pocket SiO₂=76.0±5.5, Al₂O₃=16.2±3.6, CaO=2.2±0.2, FeO=1.0±0.1, Na₂O=5.1±1.3, all wt%, n=2; kamacite Fe=93.2±1.1, Ni=4.9±0.2, Co=0.46±0.02 (wt%), n=5. Oxygen isotopes (K. Ziegler, UNM): 3 acid-washed fragments analyzed by laser fluorination gave δ¹⁸O= 7.374, 8.164, 9.305; δ¹⁷O= 3.203, 3.663, 4.288; Δ¹⁷O= -0.690, -0.647, -0.625 (linearized, all per mil, TFL slope=0.528).

Classification: Ungrouped achondrite, metal-rich. The oxygen isotope values of this meteorite plot at the high end of the ureilite trend, and it possesses olivine with Fa, Fe/Mn, Cr₂O₃, and CaO within the range of ureilites, suggesting ureilite affinity, however it lacks both pigeonite and low-Ca pyroxene.

Specimens: 20 g including a probe mount on deposit at UNM, Jay Piatek holds the main mass.