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Boxhole   contributed by Andreas Koppelt, IMCA 6161   MetBul Link


Roll Overs:     #1   #2   #3    


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View all entries for   Meteorite (5)   Andreas Koppelt (22)


Copyright (c) Andreas Koppelt.
30.2 grams.   Iron, IIIAB

TKW 500 kg. Fall not observed. Found 1937.



 


Andreas writes:
This full slice from a Boxhole individual shows a remarkable reheated rim (Alpha-2-Zone). The Widmannstätten pattern recrystallized due hot temperatures during the flight through the atmosphere of Earth. Recrystallization happens at temperatures over 750°C. Usually a reheated rim on a fresh individual of an iron meteorite is 1-2 mm thick. In this case, the rim measures 6mm at its widest!
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Found at the arrow (green or red) on the map below

 


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This Month

2 pictures in the Queue
Andreas Koppelt
 8/10/2016 6:26:49 AM
Present a neighbour partslice is to find on ebay... (no ad, I got nothing to do with the seller)
John Divelibss
 8/9/2016 8:18:32 PM
also melting points of iron and nickel are around 1500 C, and most stony materials other than the iron nickel parts melt at 800 to 1200 C, allowing for the more time needed to ablate an iron surface.
Graham Macleod
 8/9/2016 7:11:42 PM
WOW Andreas! Definitely a keeper and a beautiful Australian Meteorite. Is this reheating common or is this a rare beauty? Cheers.
John Divelbiss
 8/9/2016 7:11:11 PM
Andreas...great specimen. Yes, the inherent difference between the iron-nickel heat transfer coefficient, and a stone material mixed with iron nickel is significant enough to transfer a lot more heat inward than a stone would Good point !! Ablation time for a given surface area is likely longer too for the meta,l allowing for more heat to transfer inward based on time.
Andreas Koppelt
 8/9/2016 3:30:06 PM
Thanks for the nice words!:-) @ Michael: Almost all fresh/unweathered iron individuals with Widmannst*tten show a small reheated rim (e.g. most famous Sikhote-Alin, even some "old" unweathered Twannberg individuals). This fact is basically approved by literature (Buchwald, Handbook of Iron Meteorites, heat affected Alpha-2-Zones, pages 52, 697) @Tracy: The transformation obviously depends on the time of reheating process and - for sure - the temperature. You can find a nice Zacatecas example on Mike Farmer*s website: meteoriteguy.com/catalog/zacatecas.htm . Zacatecas 1969 was misused as an anvil and artificially reheated by torch. The Widmannst*tten pattern is still visible in some regions of the meteorite, in others it totally vanished. @John: Interesting question about other internal affects in stone meteorites. I just know Fusion crust, but no further effects. Maybe iron meteorites transmit the heat faster to the inner layers than stony meteorites. Furthermore the stone me
Bernd Pauli
 8/9/2016 3:06:59 PM
Hello Tracy, hello all, maybe it was only weakly reheated so that the original crystal pattern still "shines through"?!
Tracy Latimer
 8/9/2016 12:23:33 PM
You can still see traces of the original crystal pattern, which is a little surprising. I would have thought it would have been completely destroyed by the reheating.
Dr. Mike Reynolds
 8/9/2016 10:50:01 AM
Classy and classic! What I would call "a keeper."
Michael Mulgrew
 8/9/2016 10:49:19 AM
I am curious, what is the evidence that the reheating and recrystallization takes place during atmospheric passage? Are there published studies corroborating this theory? It seems to me that there isn't enough time for all of that to take place, but I admit to not fully understanding the process.
John Divelbiss
 8/9/2016 10:04:12 AM
Question: Do stony meteorites melt/ablate before they get to 750 degrees C? If so, then all we see is the thin layer of crust on stony meteorites as the final surface affect, and no other "internal" affects?
m schulman
 8/9/2016 8:34:21 AM
Spectacular one!! And great photography.
Twink Monrad
 8/9/2016 5:19:04 AM
What a wonderful photo!
Kally Wombacher
 8/9/2016 4:20:01 AM
Very interesting features!
 

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