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Roger Weller, geology instructor

Iron Meteorites
by Ryan Fox
Physical Geology
Spring 2013

Widmanstatten Pattern in Iron Meteotites


The Widmanstätten pattern also known as the Thomas pattern is a unique metal pattern show in Gibeon Iron Metorites. Gibeon Iron Meteorites have been thought to have come from a meteorite belt in between Earth, and Mars, and were formed when the solar system was formed around 4 billion years ago. The Gibeon meteorites were discovered by the people of Nambia during an unknown time period, and then later discovered in 1804 by an Italian man whose full name is a mystery so people call him G. Thomas.  While living in Naples in 1804 he discovered the Widmanstätten pattern in a Krasnojarsk meteorite by putting nitric acid on it. When the acid was applied to the meteorite, the pattern then exposed itself.  Due to the state Italy was in during that time period, G. Thomas didn’t get credit for his work because he was unable to get in contact with his scientific colleagues, and due to that his work was only published in Italian, and it never got out to people around Europe to see it.  Later, G. Thomas died at the age of 46 in 1808 right before another man discovered these patterns on his own. The man who discovered these patterns in the iron meteorites during 1808 was called Count Alois von Beckh Widmanstätten.  He discovered these patterns without knowing that G. Thomas had already discovered them, and because G. Thomas was never able to get his work out for scientists to see.  Widmanstätten got credit for the discovery so therefore they were named the pattern after Widmanstätten. The credit to the discovery should be shared between G. Thomas and Widmanstätten due to when they discovered it although due to it being a confusing situation the pattern goes by three different names, the Widmanstätten pattern, the Thomas structures, or the Thomson-Widmanstättan structure.

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The Widmanstätten pattern is only found in Octahedrite meteorites which is the most common structure class of iron meteorites. The meteorites are mostly composed from Iron, and nickel and it also can have other minerals in it such as copper, chromium, phosphor, and cobalt.  When cut these iron meteorites cut very strange.  Most commonly when cut the meteorites will take an Octahedron shape.   The patterns are so rare because they can only be formed after millions of years. The Widmanstätten pattern has yet to be replicated artificially by humans due to that reason.  When it is forming the different metals slow at different speeds which are called the Lamellæ formation mechanism.  What happens is that some of the metals in the core of the meteorite melt and cool at different rates due to having different melting points, and when they start to cool off they diffuse, and they then create this unique structure.

Work Cited