Widmanstätten Patterns

Widmanstätten patterns are unique structures of long nickel-iron crystals, found in most iron meteorites. The crystaline patterns become visible when the meteorites are cut, polished, and acid etched. Since nickel-iron crystals grow to lengths of several centimeters only when the molten metal cools slowly (over several million years), the presence of these patterns can be used to determine if a piece of iron is from a meteorite (as opposed to terrestrial in origin). This process was discovered in 1808 by Count Alois von Widmanstätten, who was the director of the Imperial Porcelain works in Vienna.