[meteorite-list] Zacatecas (1792) on ebay

From: Michael Fowler <mqfowler_at_meteoritecentral.com>
Date: Mon, 18 May 2009 00:36:40 -0500
Message-ID: <A09B65F4-BCC4-4F04-8B6B-7AD9CF0B00F0_at_mac.com>

Thanks Jason,

Don Edwards has a photo in the encyclopedia of meteorites, but it is
not very clear. I was trying to decide if it was the re-crystalized
1969 Zacatecas or the 1792 one. I'm inclinded to think it is the 1792
Zacatecas, but there is room for confusion.

http://www.encyclopedia-of-meteorites.com/test/Zacatecas1792_don_edwards.jpg

Mike

> 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
Received on Mon 18 May 2009 01:36:40 AM PDT