NWA 2828, Early Saharan "Aubrite" (EL3), Micromount

$5.00

NWA 2828 meteorites were first recovered out of the Saharan Desert of Morocco in 2005. At the time, it was classified as an aubrite achondrite. Subsequent analysis has shown that most of these samples were not aubrites - they were EL3 chondrites. Other finds were later paired to this meteorite strewnfield, which eventually became more widely known as Al Haggounia 001. Most of the pairings are not distinguishable from each other, but the NWA 2828 material tends to be fresher with a grey or bluer matrix material.

Refer to the photo. The black centimeter cube is shown for scale and is not included. You are purchasing a single small fragment like the one shown. Your purchase will include a labeled gemjar for safe storage.

From the Meteoritical Bulletin entry on NWA 2828 :

Northwest Africa 2828

Mauritania or Algeria

Find: December 2005

Achondrite (aubrite)

History: Purchased in December 2005 by Greg Hupé from a Moroccan dealer in Tagounite.

Physical characteristics: Thirty-six pale gray to whitish stones lacking fusion crust with a total weight of 8672 g. Several stones have exterior light orange staining, and two stones contain one or two dark brown cross-cutting veins (1–2 mm wide) of magnetic, fine-grained iron oxide and hydroxide minerals.

Petrography: (A. Irving and S. Kuehner, UWS) Monomict microbreccia, which is mostly fairly uniform but contains sporadic small, rounded clasts (up to 4 mm across). Relatively fine but variable grain size (0.3–1.5 mm), and composed predominantly of bladed grains of essentially pure enstatite (exhibiting lamellar twinning) with ~15 vol% oligoclase, accessory altered troilite with fresh, subparallel exsolution blades of daubreelite, and sporadic rounded to ellipsoidal grains of graphite (up to 1.2 mm across). Small (<0.2 mm) lobate cavities partly filled with fine-grained calcite, silica, and an Fe-bearing mineral are present in the interior of even the freshest stones, and may represent former oldhamite grains. Small grains found as inclusions within enstatite are fresh Ti-free troilite, pure Mn-alabandite, daubreelite, fresh oldhamite (some Mn-bearing), schreibersite, and very rare specks of kamacite and taenite. Minor barite and calcite are present, probably the products of terrestrial weathering.

Mineral compositions and geochemistry: Pyroxene (En99.8Wo1.4; Al2O3 = 0.21 wt%), plagioclase (An13.5–15.3 Or3.0–4.4). Oxygen isotopes: (D. Rumble, CIW) Analyses of two whole-rock fragments by laser fluorination gave, respectively, δ18O = 5.50, 5.56; δ17O = 2.89, 2.90; Δ17O = +0.001, −0.026 (all ‰).

Classification: Achondrite (aubrite). Weathering effects in most stones are limited to alteration of interior troilite and probable oldhamite, and minor orange staining and dissolution on exterior surfaces. This aubrite appears to be completely different in appearance and texture from more metal-rich enstatite-rich meteorites NWA 002NWA 1067NWA 2736, and NWA 2965.

Type specimen: A total of 20.1 g and two polished thin sections are on deposit at UWS. GHupé; holds the main mass.