This very strange cross-section view of a meteorite is a chunk of the Alvord Meteorite, discovered in Iowa in 1976. The line-crossing pattern, commonly found in iron meteorites, is known as the Widmanstätten Pattern. Image © wikimedia
The Widmanstätten pattern is forming mainly because the iron meteorite cools very slowly over the course of millions of years.
Widmanstätten patterns, also called Thomson structures, are unique figures of long nickel-iron crystals, found in the octahedrite iron meteorites and some pallasites. They consist of a fine interleaving of kamacite and taenite bands or ribbons called lamellæ. Commonly, in gaps between the lamellæ, a fine-grained mixture of kamacite and taenite called plessite can be found.
“The Alvord Meteorite was found on or around June 5, 1976, on a farm about 13 miles southeast of the Lyon County town of Alvord. Arnis History of Meteorites lists it as weighing 17.5 kg (38.5 lbs) when found and being an iron octahedrite (IVA). The find location was listed as 43º 19’ 20” N, 96º 17’ 20” W. New information indicates that the meteorite was found by Herbert Van Engen on the John Mulhall farm, T98N, R46W, Sec 09, north half, about a mile southeast of Alvord. The meteorite was eventually sold to the National Museum of Natural History, Smithsonian Institution for $800, however a slab was cut and retained by the Van Engen family as a souvenir.”