Iron, IIAB, One of the main types of iron meteorites composed almost entirely of kamacite and named for its cubic (hexahedral) cleavage of α-Fe-Ni crystals. Upon etching, hexahedrites do not display a Widmanstätten pattern, but do often exhibit fine, parallel lines called Neumann lines for their discoverer, Franz Neumann, who first studied Click on Term to Read More
(Compositionally related to group IIG)
Found 1971, recognized 1990
26° 6′ N., 106° 58′ W. This dish-shaped 58.63 kg Work 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 was found beside a mountain road 0.5 km south of Guadalupe y Calvo, Mexico. The meteorite was used as a dog bowl on a ranch in Chihuahua, Mexico until it was recognized as meteoritic and traded for a new pickup truck. Having low nickel contents of 4.5%–6.5%, hexahedrites consist of large cubic crystals of More common than taenite, both taenite and kamacite are Ni-Fe alloys found in iron meteorites. Kamacite, α-(Fe,Ni), contains 4-7.5 wt% Ni, and forms large body-centered cubic crystals that appear like broad bands or beam-like structures on the etched surface of a meteorite; its name is derived from the Greek word Click on Term to Read More. Upon etching, this meteorite class exhibits shock-induced, parallel twinning planes named ‘Neumann’ lines, but exhibits no Thomson (Widmanstätten) structure. Previously, a division of the similar magmatic irons into the IIA and IIB groups was made based on this structure, but because there is no compositional hiatus between these groups, such a division is considered arbitrary and is no longer recognized (Wasson et al., 2007).
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