IIAB Iron Meteorites
Description: Structurally, the IIAB iron meteorites are classified as hexahedrites or coarsest octahedrites, making them some of the most nickel-poor iron meteorites known. Most of them exhibit remarkable Neumann lines when etched, but no Widmanstätten figures.
Formation history & Origin: The Neumann lines do represent a shock-induced, structural deformation of the kamacite plates in IIAB irons, and they suggest an impact history for the IIAB iron meteorite parent body. Trace element abundances also suggest that the IIAB irons formed in the core of a differentiated C-type asteroid that was disrupted by several impact events.
Members: This is another well-represented group of iron meteorites consisting of about 110 members. Famous IIAB hexahedrites are Braunau, a meteorite that fell in Bohemia in 1847, and North Chile, a find from 1875, both displaying abundant Neumann lines. When considering the coarsest octahedrites, we have to mention Lake Murray, one of the oldest meteorites known. It fell about 110 million years ago and has been preserved up to this day imbedded in some ancient sandstone. Finally, we have to mention the downright notorious Sikhote-Alin, Russia, a witnessed fall from 1947. Several thousand individuals with a total weight of more than 70 tons have been recovered, and this is surely one of the most beautiful and more affordable iron meteorites on the collector's market.