Most iron meteorites contain very interesting patterns in their cross-section (after cleaning, but also on the outside) - so-called Widmanstätten patterns, which look like a regular grid that appears on the cross-section of an iron meteorite if it is etched with acid, which accentuates the patterns. They are related to the meteorite's crystal structure, made up of plate-like crystals of kamacite and taenite. Both minerals are composed of iron and nickel, i.e. they do not appear on almost pure iron meteorites (ataxites) such as Dronino.
The patterns were discovered in 1808 by Count A. J. von Widmanstätten and are clear evidence of extraterrestrial origin and have never been observed in terrestrial iron. It has been suggested that they were formed during the cooling of the metal in weightlessness over millions of years.
Among the meteorites with the most consistent Widmanstätten patterns are Muonionalusta, Gibeon and Seymchan. Interestingly, different meteorites also have very different thicknesses of the "lines" that make up the patterns. To make them visible, it is first necessary to polish the meteorite section and then etch the surface with dilute nitric acid, ideally a solution of nitric acid in methanol (called nital).