Northwest Africa 13621 (NWA 13621)

Mali

Purchased: 2020 Jan-Sep

Classification: Lunar meteorite (feldspathic breccia)

History: Additional stones (total 49 pieces) very similar to the unusual and distinctive specimens classified as Tisserlitine 001, and which were recovered at the same location in Mali, were acquired from several dealers by John Higgins (500 g), Fabien Kuntz (311 g), Dirk Ross (407 g), and an Algerian team represented by David Lehman (390 g). Comparative assessment and analyses of samples from each of these batches of stones were conducted to confirm their pairing with the previous material.

Physical characteristics: Most of the specimens have a flattened slab-like form and all have distinctive medium-brown, "knobby" exterior surfaces coated by desert patina. Interiors of stones are multi-colored (pink, tan, gray) with some darker gray and white clasts and small grains of metal.

Petrography: (A. Irving, UWS and P. Carpenter, WUSL) Breccia composed of mineral clasts of anorthite, olivine, augite and pigeonite, plus sparse lithic clasts of microcrystalline anorthosite with fine grained mafic phases, are set in a fine grained microvesicular matrix containing accessory altered kamacite, troilite and rare pentlandite together with secondary calcite and barite. Olivine grains have been partially replaced by inhomogeneous phyllosilicate-rich assemblages characterized by systematically low oxide analytical sums (89-94 wt.% ) and deficiency in manganese (yielding elevated FeO/MnO ratios of 119-122).

Geochemistry: Olivine (Fa_24.5-40.6, FeO/MnO = 77-98, N = 7), pigeonite (Fs_20.6-24.0Wo_5.8-6.8, FeO/MnO = 46-50, N = 3), augite (Fs_14.1-14.4Wo_37.3-41.4, FeO/MnO = 50-54, N = 3), anorthite (An_94.6-97.5Or_0.0-0.1, N = 3).

Classification: Lunar (feldspathic regolithic breccia, partially hydrothermally-altered). The colors, textures, mineral compositions and distinctive secondary alteration in these specimens establish beyond doubt that they are paired stones to Tisserlitine 001.

Specimens: 22.2 g including a polished endcut and one polished mount at UWB; 25 g plus one polished thin section at PSF; remaining material with Mr. J. Higgins, Kuntz, Mr. D. Ross and Mr. D. Lehman.