NWA 7831

Saguia el Hamra, Western Sahara
Find, March 2013

Achondrite, Diogenite
Many pieces, total weight around 1,6kg,
Biggest piece weight 1250g

Found buried in the ground near Chouichiyat on March 3, 2013, and excavated by a team of local people.

Physical characteristics:
A single large mass (at least 20 kg) composed of yellow-green crystalline material with pale orange weathering products along numerous fractures. Much of the material disintegrated into fragments upon excavation.

(A. Irving and S. Kuehner, UWS) The specimen is composed almost entirely of translucent, yellow-green orthopyroxene with very sparse, tiny included grains of Ni-free metal, troilite, chromite, anorthite, silica polymorph and clinopyroxene. Secondary pale orange, clay-like deposits from terrestrial weathering are present along thin fractures.

Orthopyroxene (Fs28.1-28.3Wo3.0-3.3; FeO/MnO = 29-31), clinopyroxene (Fs10.9Wo43.1, FeO/MnO = 26). Oxygen isotopes (K. Ziegler, UNM): analyses of acid-washed orthopyroxene by laser fluorination gave, respectively, δ17O = 1.677, 1.793, 1.810; δ18O = 3.680, 3.879, 3.875; Δ17O = -0.266, -0.255, -0.236 per mil.

44.5 g of material is on deposit at UWB. The remainder is held by several anonymous collectors.

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