Northwest Africa 11531 (NWA 11531)

(Northwest Africa)

Purchased: 2016

Classification: HED achondrite (Diogenite)

History: A single stone weighing 35.2 g was found in Morocco prior to 2016. J. Donald Cline and John Sinclair acquired the sample from a meteorite dealer at the Tucson Gem and Mineral Show in February of 2017.

Physical characteristics: Sample is mottled dark-greenish-gray colored, non-magnetic and tabular in shape. Sample has an obvious brecciated texture composed of light-colored clasts in a darker groundmass. One side of sample has an orange coating and is notably more flattened than the opposite side which is quite irregular.

Petrography: Description and classification (A. Love, App): Sample is a breccia composed of dominant sub-rounded to angular fragments of orthopyroxene (up to 1650 µm, average length 880 µm), olivine (~2 vol%), plagioclase, glass, chromite, FeS, FeNi, minor phosphate and Si-polymorph metal set in matrix of similar finer-grained Opx, olivine and interstitial plagioclase. Some Opx grains contain olivine melt inclusions. Sample is transected by networks of opaque shock veins.

Geochemistry: (A. Love, App) Low Ca-Opx (Fs_21.4±0.7Wo_2.5±0.4, FeO/MnO=26.3-28.4, N=18), Olivine (Fa_22.8±0.4, FeO/MnO=46.8-49.3, N=8), plagioclase An_85.7±1.3Or_0.2±0.0, N=5).

Classification: HED (diogenite).

Specimens: PARI holds the main mass. A slice and several small fragments weighing 7.1 g and a polished thin section are on deposit at App.