[meteorite-list] Brahin - legit?

From: Paul <lenticulina1_at_meteoritecentral.com>
Date: Thu Apr 22 10:21:09 2004
Message-ID: <20030728134159.24664.qmail_at_web21411.mail.yahoo.com>

On Mon, 28 Jul 2003,
Pekka Savolainen

>Hello to all,
>
>at the moment IŽd buy Brahins from a
>reliable seller,usually all IMCA members
>are that...;- Also Finmet on eBay
>have sure pure and fresh pieces.
>(Not an AD.)

>The point of view is, there is still
>150 kg:s of Shirokovsky pseudo left,
>and if you are not familiar with
>Brahin and the seller is unknown, it
>seems to me, there is a possibility to
>have a piece of this stuff, not a
>big one, but anyway.

One thing to look at is the roundness
and shape of the olivine grains. The
Shirokovsky pieces that I saw on web
pages all apparently exhibit mostly
very angular to subangular olive grains.
In contrast, the olivine in certified
pallasites that I have observed have
largely subrounded and rounded grains.
Also, the typical shape of the olivine
in the Shirokovsky pieces appear to
vary from equant to platy and elongate.
Again, in contrast, the pallasites
that I have observed consist largely
of equant grains. Finally, it appears
that some pallasites have some olivine
grains that are coalesced, grown
together, something, I have yet to
see in a Shirokovsky piece. I suspect
that these differences reflect how the
olivine grains in pallasites and
Shirokovsky pieces were produced.

If a person was to quantify the
roundness and shape of the olivine
grains, in cross-section of course,
I suspect that pallasites and
Shirokovsky pieces could be differentiated
from each other on their hand specimen
characteristics. All a person would
need to do this work is collect and
analyze a number of 1:1 scale scans
at 350 dpi of the face of cut sections
of various pallasites and Shirokovsky
pieces. Once this was figured out,
then blind tests could be done using
similar scans from other pieces to
empirically test how well such a
methodlogy wouldwork.

Yours,

Paul
Baton rouge, LA

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Received on Mon 28 Jul 2003 09:41:59 AM PDT