Widmanstätten patterns, also called Thomson structures, are historically figures of long - crystals, found in the   and some. They consist of a fine interleaving of  and  bands or ribbons called . Commonly, in gaps between the lamellae, a fine-grained mixture of  and  called  can be found. Widmanstätten patterns describe features in modern steels, titanium and zirconium alloys.Discovery[]In 1808, these figures were named after , the director of the Imperial Porcelain works in . While flame heating ,Widmanstätten noticed color and  zone differentiation as the various iron alloys oxidized at different rates. He did not publish his findings, claiming them only via oral communication with his colleagues. The discovery was acknowledged by , director of the Vienna Mineral and Zoology Cabinet, who named the structure after Widmanstätten.However, it is now believed that full credit for the discovery should actually be assigned to  as he published the same findings four years earlier.Working in Naples in 1804,  treated a   with  in an effort to remove the dull patina caused by oxidation. Shortly after the acid made contact with the metal, strange figures appeared on the surface, which he detailed as described above. Civil wars and political instability in southern Italy made it difficult for Thomson to maintain contact with his colleagues in England. This was demonstrated in his loss of important correspondence when its carrier was murdered. As a result, in 1804, his findings were only published in French in the Bibliothèque Britannique. At the beginning of 1806,  invaded the  and Thomson was forced to flee to  and in November of that year, he died in  at the age of 46. In 1808, Thomson's work was again published posthumously in Italian (translated from the original English manuscript) in Atti dell'Accademia Delle Scienze di Siena. The  obstructed Thomson's contacts with the scientific community and his peregrinations across Europe, in addition to his early death, obscured his contributions for many years.The most common names for these figures are Widmanstätten pattern and Widmanstätten structure, however there are some spelling variations:Moreover, due the discover priority of , several authors suggested to call these figures Thomson structure or Thomson-Widmanstätten structure.Lamellae formation mechanism and  form   at temperatures below the ; these alloys are . At temperatures below 900 to 600 °C (depending on the Ni content), two alloys with different nickel content are stable: kamacite with lower Ni-content (5 to 15% Ni) and taenite with high Ni (up to 50%).   have a nickel content intermediate between the norm for  and ; this leads under slow cooling conditions to the precipitation of kamacite and growth of kamacite plates along certain in the taenite crystal lattice.The formation of Ni-poor kamacite proceeds by diffusion of Ni in the solid alloy at temperatures between 700 and 450 °C, and can only take place during very slow cooling, about 100 to 10,000 °C/Myr, with total cooling times of 10 Myr or less. This explains why this structure cannot be reproduced in the laboratory.The  patterns become visible when the meteorites are cut, polished, and acid etched, because  is more resistant to the acid. In the picture shown, the broad white bars are kamacite (dimensions in the mm-range), and the thin line-like ribbons are taenite. The dark mottled areas are called plessite.