NWA 1912

MesosideriteOne of two main types of stony-iron meteorite, the other being pallasites. Mesosiderites are a mixture of approximately 50% basaltic, gabbroic and orthopyroxenitic silicates and 50% Ni-Fe metal and sulfides. The name derives from the Greek "mesos" meaning "middle" or "half" and "sideros" for "iron;" hence "half-iron". The silicates are Click on Term to Read More, subgroup 2C (subgroup 2B in Metbull 88)
Found 2002, no coordinates recorded

A very small fusion-crusted stone weighing only 13.52 g was purchased in Erfoud, Morocco by M. Farmer in March 2003. Analysis and classification was completed at Northern Arizona University. Although the MetBull #88 lists NWA 1912 as belonging to subgroup 2B, it exhibits only minor recrystallization and has a matrixFine grained primary and silicate-rich material in chondrites that surrounds chondrules, refractory inclusions (like CAIs), breccia clasts and other constituents. Click on Term to Read More composed predominantly of large orthopyroxeneOrthorhombic, low-Ca pyroxene common in chondrites. Its compositional range runs from all Mg-rich enstatite, MgSiO3 to Fe-rich ferrosilite, FeSiO3. These end-members form an almost complete solid solution where Mg2+ substitutes for Fe2+ up to about 90 mol. % and Ca substitutes no more than ~5 mol. % (higher Ca2+ contents occur Click on Term to Read More grains along with some plagioclaseAlso referred to as the plagioclase feldspar series. Plagioclase is a common rock-forming series of feldspar minerals containing a continuous solid solution of calcium and sodium: (Na1-x,Cax)(Alx+1,Si1-x)Si2O8 where x = 0 to 1. The Ca-rich end-member is called anorthite (pure anorthite has formula: CaAl2Si2O8) and the Na-rich end-member is albite Click on Term to Read More, features that are consistent with assignment to subgroup 2C. Furthermore, it is considered likely that NWA 1912 is a member of the NWA 1827 pairing group, assigned to subgroup 2C (Bunch et al., 2004).

Northwest Africa 1912 is an unshocked meteoriteWork in progress. A solid natural object reaching a planet’s surface from interplanetary space. Solid portion of a meteoroid that survives its fall to Earth, or some other body. Meteorites are classified as stony meteorites, iron meteorites, and stony-iron meteorites. These groups are further divided according to their mineralogy and Click on Term to Read More (S1) that shows only minor signs of weathering. The specimen in the photo above is a 0.64 g partial slice, which exhibits green orthopyroxene fragments in a metallic matrix, along with lesser amounts of anorthitic plagioclase, chromiteBrownish-black oxide of chromium and iron (Cr-Fe oxide), Cr2FeO4, found in many meteorite groups. Click on Term to Read More, troiliteBrass colored non-magnetic mineral of iron sulfide, FeS, found in a variety of meteorites. Click on Term to Read More, and silicaSilicon dioxide, SiO2..