[meteorite-list] Zacatecas (1792) on ebay

From: Jason Utas <meteoritekid_at_meteoritecentral.com>
Date: Sun, 17 May 2009 22:10:59 -0700
Message-ID: <93aaac890905172210t1a4fedabk52a62dbfaae2d336_at_mail.gmail.com>

Hello Mike,
Indeed, that's not a piece of the more common Zacatecas (1969).
See here; that iron is clearly recrystallized:

http://www.nyrockman.com/museum/zacatecas-1462.htm

While I haven't been able to find a picture of the etch of the
Zacatecas (1792) iron, I was able to find this picture of the main
mass:

http://commons.wikimedia.org/wiki/File:Zacatecas_(1792)_meteorite.jpg

There is more than one Zacatecas!
Regards,
Jason

On Sun, May 17, 2009 at 9:52 PM, Michael Fowler <mqfowler at mac.com> wrote:
> I collect ungrouped irons, and am looking for a slice of Zacatecas (1792) an
> ungrouped iron.
>
> The specimen on ebay:
>
> http://cgi.ebay.com/Meteorite-ZACATECAS-1792-perfect-etched-slice-12-3g_W0QQitemZ270389277772QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item3ef474f44c&_trksid=p3286.c0.m14&_trkparms=66%3A2%7C65%3A3%7C39%3A1%7C240%3A1318%7C301%3A1%7C293%3A5%7C294%3A50#ebayphotohosting
>
> does not in my opinion look like the photo in Buchwald, or match his
> description:
>
> "Zacatecas is remarkable in that it belongs to the rather few
> polycrystalline iron meteorites. ?The grain size ranges from 1 to 5 cm, a
> variation which is partly due to the random sectioning through many almost
> equiaxial grains. ?....... ? The grain boundaries are also conspicuous
> because of the copious development of very irregular 1-3 mm wide zones of
> swathing kamacite. ?This kamacite was nucleated by the troilite and
> schreibersite precipitates, and by the boundary itself, and grew
> significantly before the bulk of the grains transformed during the primary
> cooling period.
> ......
> Zacatecas may have shown a kamacite bandwith ot one time of .6 -1.0 mm, but
> since all taenite eventually disappeared and significant grain growth in the
> kamacite took place, no well defined Widmanstatten pattern is present now.
> ?In this respect, Zacatecas resembles New Baltimore, Santa Rosa and
> Chihuahua City."
>
> So in short, no well defined Widmanstatten pattern, unlike the photo in the
> ebay ad.
>
> Would anyone like to comment?
>
> Thanks,
>
> Mike Fowler
> Chicago
>
> ebay--starsandrocks
>
>
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Received on Mon 18 May 2009 01:10:59 AM PDT