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Widmanstätten pattern
Widmanstätten patterns, also called Thomson structures, are historically 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 ''lamellae''. Commonly, in gaps between the lamellae, a fine-grained mixture of kamacite and taenite called plessite can be found. Widmanstätten patterns describe features in modern steels,〔DOMINIC PHELAN and RIAN DIPPENAAR: Widmanstätten Ferrite Plate Formation in Low-Carbon Steels, METALLURGICAL AND MATERIALS TRANSACTIONS A, VOLUME 35A, DECEMBER 2004—3701〕 titanium and zirconium alloys.
==Discovery==
In 1808, these figures were named after Count Alois von Beckh Widmanstätten, the director of the Imperial Porcelain works in Vienna. While flame heating iron meteorites,〔O. Richard Norton. ''Rocks from Space: Meteorites and Meteorite Hunters''. Mountain Press Pub. (1998) ISBN 0-87842-373-7〕 Widmanstätten noticed color and lustre 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 Carl von Schreibers, director of the Vienna Mineral and Zoology Cabinet, who named the structure after Widmanstätten.〔John G. Burke. ''Cosmic Debris: Meteorites in History''. University of California Press, 1986. ISBN 0-520-05651-5〕
However, it is now believed that full credit for the discovery should actually be assigned to G. Thomson as he published the same findings four years earlier.〔〔〔O. Richard Norton. ''The Cambridge Encyclopedia of meteorites''. Cambridge, Cambridge University Press, 2002. ISBN 0-521-62143-7.〕
Working in Naples in 1804, Thomson treated a Krasnojarsk meteorite with nitric acid 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''.〔〔Gian Battista Vai, W. Glen E. Caldwell. (origins of geology in Italy'' ). Geological Society of America, 2006, ISBN 0-8137-2411-2〕〔F. A. Paneth. ''The discovery and earliest reproductions of the Widmanstatten figures''. Geochimica et Cosmochimica Acta, 1960, 18, pp.176-182〕 At the beginning of 1806, Napoleon invaded the Kingdom of Naples and Thomson was forced to flee to Sicily〔 and in November of that year, he died in Palermo 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''.〔G.Thomson. (di G.Thomson sul ferro Malleabile trovato da Pallas in Siberia'' ). Atti dell'Accademia Delle Scienze di Siena, 1808, IX, p. 37.〕 The Napoleonic wars 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.
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