[meteorite-list] Etching Estherville

[bernd.pauli at paulinet.de]

Hello Mike and List!

"I just obtained a nice slice with a bleb about 20mm in diameter and we etched this
and a faint pattern is seen. Is it possible that this is a Widmanstätten pattern?"

See NORTON O.R. (2002) The Cambridge Encyclopedia of Meteorites 
(Cambridge University Press, p. 158): "Remarkably some of the larger metal
nodules when polished and etched show Widmanstätten structure typical of
octahedrites".

O.R. Norton also mentions a "nickel content of between 7 and 10%,
[which] is the nickel content of octahedrite meteorites."

So no need to be surprised as Estherville has a nickel content of 9.0%.

"I am not sure if the metal melted and cooled properly
to allow the kamacite and taenite to separate"

McSWEEN H.Y. (1999) Meteorites and Their Parent
Planets (Cambridge University Press, Glossary, p. 212):

"The resulting mixture was buried deeply, so that slow cooling produced
a Widmanstätten pattern in the metal. The cooling rates for mesosiderites
.. are exceptionally slow, less than half a degree per million years."

Best Estherville wishes,

Bernd