Hexahedrite

One of the main types of iron meteorites composed almost entirely of kamaciteMore 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 and named for its cubic (hexahedral) cleavage of α-Fe-Ni crystals. Upon etching, hexahedrites do not display a Widmanstätten patternCharacteristic cross-hatched pattern visible on the surface of octahedrites, pallasites and even large metal blebs in chondrite melts and mesosiderite nodules after polishing and etching with an acid solution like nital (nitric acid in solution with ethanol). The acid will preferentially etch the iron based on its nickel content - Click on Term to Read More, but do often exhibit fine, parallel lines called Neumann linesFine twinning boundaries seen as parallel lines running along the plane of kamacite crystals of hexahedrite iron meteorites. They may appear also in octahedrite iron meteorites provided the kamacite phase is about 30 mm wide. They can be seen after a polished meteorite cross-section is treated with acid. The lines Click on Term to Read More for their discoverer, Franz Neumann, who first studied them in 1848. These lines represent shock-induced, structural deformation of the kamacite plates, and reveal an impact history for the hexahedrite parent bodyThe body from which a meteorite or meteoroid was derived prior to its ejection. Some parent bodies were destroyed early in the formation of our Solar System, while others like the asteroid 4-Vesta and Mars are still observable today. Click on Term to Read More, at least for the hexahedrites related to chemical group IAB.

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