Widmanstätten Pattern

Characteristic cross-hatched pattern visible on the surface of octahedrites and pallasites after polishing and etching with nital (nitric acid in solution with ethanol). It is due to an intergrowth of crystals of Ni-rich taenite and Ni-poor kamacite. It is named after its discoverer, Austrian mineralogist Alois von Beckh Widmanstätten (1754-1849).

Image source: http://meteorites.wustl.edu/id/metal.htm.