Northwest Africa 3138

Morocco

Purchased 2004 February

Achondrite (eucrite)

A complete, very fresh stone (132 g; 63 mm x 43 mm x 40 mm) with thin black fusion crust was purchased from a Moroccan dealer at the Tucson Gem and Mineral Show by P. Mani (Mani) in 2004 February.  Classification and mineralogy (A. Irving and S. Kuehner, UWS):  Ophitic texture. Mainly inverted pigeonite and calcic plagioclase (An_88.7-89.6Or_0.3-0.4) with accessory ilmenite, silica polymorph, Ti-Al-bearing chromite, orthopyroxene (as inclusions within plagioclase), and sparse troilite (mainly as blebs within silica) and altered Ni-poor iron metal.  Pyroxene grains consist of coarse lamellae of augite (Fs_30.6Wo_37.2., FeO/MnO = 28.1) within orthopyroxene (Fs_62.7Wo_1.3., FeO/MnO = 33.0), and coarse lamellae of orthopyroxene (Fs_62.1Wo_1.7., FeO/MnO = 31.1) within augite (Fs_23.5Wo_42.1., FeO/MnO = 30.6).  Minor secondary calcite laths occur around silica along a crack. Although the pyroxene and plagioclase compositions in this specimen are almost identical to those in NWA 3137, the textures are quite different, and these two stones are not paired.  Specimens: type specimens, 20.7 g, and one polished thin section, UWS; main mass, Philip Mani, 901 Sonterra Blvd., Suite 316, San Antonio, TX  78258.