Description
Northwest Africa 13190 (NWA 13190)
Algeria
Find: 2019
Classification: Martian meteorite (Shergottite)
History: Purchased in 2019 by Miguel Angel Contreras Gomez from a meteorite dealer in Algeria.
Physical characteristics: This sample has a weathered fusion crust exterior, however the interior remains fresh.
Petrography: (D. Sheikh, FSU) Sample is a diabase having a predominantly subophitic texture composed of complexly zoned, tabular and prismatic (sometimes twinned) chadacrysts of subcalcic augite and pigeonite (Av. 330±50 µm, up to 1mm, 60 vol%) contained within larger oikocrysts of maskelynite (Av. 800±100 µm, up to 2 mm, 40 vol%). Accessory phases include titanomagnetite (some Cr rich), ilmenite, silica, Si-Al-K-Na rich glass, merrillite, and pyrrhotite.
Geochemistry: Subcalcic augite (Fs32.3±6.6 Wo30.7±2.3, range Fs21.7-47.7 Wo25.4-35.2, FeO/MnO=34±6, n=37) pigeonite (Fs52.7±8.5 Wo14.4±2.3, range Fs30.6-72.3 Wo10.0-19.3, FeO/MnO=36±4, n=54) maskelynite (An48.9±5.1 Or1.9±1.0, range An41.4-55.7 Or0.3-3.8, n=43).
Classification: Martian (shergottite, diabasic) Silicate chemistry, the presence of maskelynite, FeO/MnO ratios of pyroxenes, and magnetic susceptibility provide support for classification as shergottite. Average grain sizes of pyroxenes and maskelynite larger than that of basaltic shergottites, but smaller than gabbroic shergottites, hence diabasic.
Specimens: 10.02 grams at UCLA; main mass with Miguel Angel Contreras Gomez.
