[meteorite-list] Very strange Nickel Iron structure in a NWA chondrite

From: abudka at nycap.rr.com <abudka_at_meteoritecentral.com>
Date: Tue, 19 Oct 2010 12:42:22 -0400
Message-ID: <20101019164222.BICPW.262284.root_at_cdptpa-web25-z02>

Hello Listers,

The nickel-iron structures seen in the droplets at

http://s345.photobucket.com/albums/p384/m42protosun/Bubble%20iron/
 
m42protosun

are dendrites.

A ?dendrite indicates a linear, branched structure of which the arms are all parallel to specific
crystallographic directions? (1). AND, dendritic morphology (of which there are
various kinds) always indicates non-equilibrium solidification. These droplets must have solidified under different gravitational conditions than the 1g we know on earth (perhaps
microgravity?).
 
While unusual ? but not unknown in the meteoritics world, such structures are
familiar to casting metallurgists. Iron dendrites found in pockets and veins in
the Yanzhuang H6 meteorite are characterized in papers by Li Z. et al. (2) and
Brooks et Al. (3).
 
A though experiment: Thicken these dendritic branches, give them more melt
liquid and more time to grow in low gravity ? and what do you have? The
Widmanst?tten structure!
 
An alternate interpretation of the meteoritic Widmanst?tten structure as a
primary crystallization, 3-dimensional dendritic structure solidified under
non-equilibrium microgravity conditions is found at my website,
 
http://meteormetals.com/
 
For background on the circular reasoning behind how meteoritic Widmanst?tten
morphology became the Widmanst?tten mechanism, click Learn More at my website.
 
 
Phyllis Budka
abudka at nycap.rr.com
 
References:
1. Chalmers, Bruce, ?Principles of Solidification Processing,? 1977 edition, p.
92.
2. Li Z., Xie X., and Zhang D. Meteoritics 27, 249.
3. Brooks, C., Biery, N., Li Z., Xie X., and Zhang D., Materials
Characterization 35:165-174 (1995).

------------------------------------------
Hello lists, with my new Bresser microscope I have detected a structure in
metalflakes which I can not explain. Has any one seen such a structure in
meteorites or documentation where it is explalned?
Look at
 
http://s345.photobucket.com/albums/p384/m42protosun/Bubble%20iron/
 
m42protosun


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Received on Tue 19 Oct 2010 12:42:22 PM PDT