Northwest Africa 8739 (NWA 8739)

(Northwest Africa)

Purchased: 2013

Classification: HED achondrite (Eucrite, polymict)

History: Purchased by Blaine Reed from Eegooblago Meteorites at the Denver Gem and Mineral Show 2013.

Physical characteristics: Single stone, smooth brown weathered exterior. A saw cut reveals a breccia with scattered clasts up to ~1 cm set a in fine-grained, gray, groundmass.

Petrography: (C. Agee, UNM) Microprobe examination of a polished mount shows ~55% pyroxene and ~40% plagioclase. Accessory silica, troilite, chromite, ilmenite, and Fe-metal. Several different microtextures are present; there are numerous fragmental pyroxene and plagioclase grains up to ~300 μm, clasts with quench mesostasis and skeletal pyroxenes, clasts with acicular plagioclase or pyroxene intergrowths. Most pyroxenes show strong igneous zoning with En-rich cores and Fs/Wo-rich rims, however there is also a minor population of pyroxenes that appear to be more equilibrated with fine exsolution lamellae.

Geochemistry: (C. Agee and N. Muttik, UNM) EMPA. Pyroxene Fs_45.6±10.9Wo_10.1±3.0, Fe/Mn=31±2, n=25; plagioclase Or_0.6±0.4Ab_10.3±3.6An _89.1±4.0, n=4. Oxygen isotopes (K. Ziegler, UNM): acid-washed material analyzed in 2 replicates by laser fluorination gave, respectively δ¹⁸O=3.420, 2.990; δ¹⁷O=1.508, 1.312; Δ¹⁷O= -0.298, -0.267 (all per mil).

Classification: Achondrite (polymicy eucrite) Unequilibrated basalt with a range of pyroxene compositions consistent with Type-2 eucrites (Takeda and Graham, 1991); a polymict breccia similar in texture and composition to Pasamonte.

Specimens: 20.0 g including a probe mount on deposit at UNM, Reed holds the main mass.