[meteorite-list] Shirokovsky Texture - A Red Flag As to Its Origin??

From: Paul Heinrich <lenticulina1_at_meteoritecentral.com>
Date: Thu Apr 22 10:22:35 2004
Message-ID: <20030608221223.88525.qmail_at_web21413.mail.yahoo.com>

I have been looking at a number of pictures of
fragments of Shirokovsky that were shown on
various web pages and pictures of pallasites.
After comparing them, there appears to be, in
my opinion, a rather drastic difference in the
texture of the olivine grains within each.. In the
pallasites, indvidual grains are equant and either
rounded or euhedral. Also, in the pallasites, a
person can find examples of olivine grains that
have coalesced together.

Examples of this texture can be seen at:

http://www.meteoriteman.com/collection/thiel.htm
http://www.meteoriteman.com/collection/dora.htm
http://www.meteoriteman.com/collection/mtvernon.htm
http://meteorites.asu.edu/pallasite.jpg

In comparison, pictures of the pieces of
Shirokovsky that I have found have a different
texture. the olivine crystals are far more angular
and variable in outline than found in the pallasites,
for which I found pivtures. In fact, some of the
olivine pieces in pictures of Shirokovsky are even
flat rectagular blades quite unlike anything seen
in true pallasites. In addition, I don't see any of
the merged / coalesced olivines seen in other,
Overall, the Shirokovsky has the apperance of a
terrazzo floor made up of fragmented rocks.
This is suggestive of fragmented chips of olivine
that have been cemented together by the matrix.

The difference in the texture of the olivine in the
pallasites and the Shirokovsky pseudometeorite is
quite striking. The texture, outline, distribution of
the olivine grains distinguish Shirokovsky as being
different from many pallisites. Also, the angular
and highly variable shape of the olivine grains
in the Shirokovsky suggest some sort natural or
artificial olivine breccia. Although might be / are
pallasites that are breccias, it seems like the
texture of the Shirokovsky pseudometeorite
should have raised a red flag as to its nature.

Yours,

Paul
Baton Rouge, LA


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Received on Sun 08 Jun 2003 06:12:23 PM PDT