Northwest Africa 5349 (NWA 5349)

(Northwest Africa)

Purchased: Jan 2008

Classification: HED achondrite (Eucrite, polymict)

History: The main mass holder purchased the sample in Zagora, Morocco.

Physical characteristics: This meteorite consists of a single stone weighing 445 g. Dark fusion crust covers one rounded side, while the other side is an irregular broken surface. Light-colored (white, beige) and black inclusions set in a dark gray matrix are visible in both the broken exterior and cut interior surfaces.

Petrography: (Melinda Hutson and Alex Ruzicka, Cascadia). In thin section, this meteorite shows lithic and mineral clasts which vary in size and texture set in a groundmass of angular grains. The three largest clasts (3-5 mm) are basaltic with mineral grains and clasts set in a granular matrix. Smaller clasts are mainly basaltic with textures varying from granular to subophitic. Large low-Ca pyroxene mineral clasts that comprise a diogenitic component are present and make up less than 10% of the section. Large feldspar mineral clasts (0.2-1 mm) are present. These feldspar clasts display a variety of textures, including triple junctions, clear twinned feldspar intergrown with cloudy feldspar, grains displaying mosaic extinction, and twinned feldspars with microfaults. No maskelynite was observed, but notable shock effects in low-Ca pyroxene (mosaic extinction) and plagioclase (recrystallization) are evident. Six clasts larger than 0.1 mm are largely opaque in transmitted light and contain silicate subclasts as well as many tiny oxide and sulfide inclusions (droplets and veins). A silicate vein containing small rounded opaques is interpreted as a shock vein. A couple of metal grains with minor oxide rims (weathering products) were observed.

Geochemistry: (Melinda Hutson and Alex Ruzicka, Cascadia; Ilya Bindeman, UOr). EMPA analyses: Mg-rich low-Ca pyroxene (Wo_1.6-5.3 En_60.5-78.1 Fs_20.0-36.8) Fe/Mn = 29.9 ± 1.8; intermediate low-Ca pyroxene (Wo_1.0-4.0 En_49.3-55.4 Fs_41.0-48.8) Fe/Mn = 32.1±0.8; Fe-rich low-Ca pyroxene (Wo_1.6-4.7 En_30.0-40.6 Fs_55.9-66.0) Fe/Mn = 31.1±0.8; pigeonite (Wo_5.6-19.1 En_31.3-48.4 Fs_41.0-60.6) Fe/Mn = 31.7±1.3; and augite (Wo_42.1-43.5 En_28.0-30.1 Fs_27.9-29.4) Fe/Mn = 34.1±2.5; plagioclase (An_88.4±2.7, Ab_11.3±2.5, n=33). Oxygen isotopes (whole rock): δ¹⁸O = 3.80±0.03 ‰, δ¹⁷O = 1.73±0.06 ‰, and Δ¹⁷O = -0.264±0.045 ‰ .

Classification: Achondrite (polymict eucrite). Minimal weathering and moderate shock.

Specimens: 21 g and one thin section are on deposit at Cascadia. Thompson holds the main mass.