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Surface Features of Irons

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#1 lee14

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Posted 05 February 2019 - 03:31 PM

Iron meteorites commonly display a number of surface features that are a function of several factors, generally in combination. Entry velocity, composition, height of breakup, fragment size, and type of explosion all contribute to the final appearance. Large falls can have more than one breakup, resulting in a wider spectrum of features. Sikhote-Alins are a prime example, and specimens fall into two categories. Most prized are the regmaglypted stones, which broke up higher in the atmosphere allowing an overall smoothing of the surface. Small super heated atmospheric eddies 'scooped' out the thumbprint-like depressions, often covering the entire specimen. Sikhote-Alin 'shrapnel' formed from a later atmospheric breakup, with insufficient time to produce smoothly defined regmaglypts. The image here is of a 67g Canyon Diablo, with features consistent with the shrapnel type.

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  • 67g Canyon Diablo.jpg

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#2 lee14

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Posted 05 February 2019 - 03:35 PM

This is a 567g Canyon Diablo, showing a sharp edge formed at breakup, bordered by shallow, curved depressions. Insufficient atmospheric heating prevented the formation of regmaglypts and kept that 'knife' edge intact.

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  • 567g Canyon Diablo b.jpg

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#3 lee14

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Posted 05 February 2019 - 03:37 PM

Finally, this is a 748g Canyon Diablo whose travel path allowed for a general smoothing, but produced only very shallow regmaglypts.

 

Lee

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  • 767g Canyon Diablo.jpg

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#4 lee14

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Posted 05 February 2019 - 04:03 PM

This is a 32g Sikhote-Alin, with perfect regmaglypts covering the entire surface. Also present is a true fusion crust, rare in iron specimens, but not uncommon in Sikhote because it was a relatively recent fall.

 

Lee

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  • 32g Sikhote-Alin comp.jpg

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#5 lee14

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Posted 05 February 2019 - 04:06 PM

Lastly, a 99g example of Sikhote-Alin shrapnel. Breakup occurred later in the atmosphere, preventing surface melting.

 

Lee

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  • 99g Sikhote c comp.jpg

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#6 hfjacinto

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Posted 05 February 2019 - 08:37 PM

Lee,

Great pictures! I haven’t purchased any meteorites in a while but looking at your pictures makes me want a few more!
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#7 lee14

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Posted 06 February 2019 - 08:19 AM

Lee,

Great pictures! I haven’t purchased any meteorites in a while but looking at your pictures makes me want a few more!

 

Thanks! It's the wide variety of naturally produced features, particularly with a specific fall, that helps drive that urge to acquire more pieces. I'm amazed at the amount of Canyon Diablo material currently available at reasonable prices, despite the long running ban on collection. Apparently more than a few dealers had stockpiled large numbers of specimens. The 748g piece above is the largest I have in my own collection, I stabilized it with a chemical process to eliminate the terrestrially introduced chlorides, as it was showing signs of 'lawrencite disease'. The other two I kept in 'as found' condition.

 

Lee


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#8 Kent10

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Posted 08 February 2019 - 06:18 PM

Thanks for the pictures and notes, Lee.  I enjoyed it.  I still am buying meteorites.  Not as many as I used to but I still enjoy looking and buying when I see something that might be different from what I already have.  I have a problem in that I can't sell any.  I think I would miss them.


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#9 rdaniel

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Posted 08 February 2019 - 07:09 PM

..." despite the long running ban on collection." Who banned collection?



#10 lee14

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Posted 08 February 2019 - 09:17 PM

Searching on state or state trust land requires a permit, which collector friends tell me are difficult or impossible to obtain. Collecting on private land is at the discretion of the land owners, and they no longer allow searches.

 

Lee




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