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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