[meteorite-list] Deformed Gibeon patterns

From: capricorn89 <capricorn89_at_meteoritecentral.com>
Date: Thu Apr 22 10:02:30 2004
Message-ID: <001c01c1cec1$494ede40$df36b2d1_at_earthlink.net>

Bernd wrote: <<As for this wedge-shape piece with no pattern at all, I can
only guess
 that it is a severely heated, melted, and recrystallized inclusion or it
 might be a plessitic field...I have been waiting here for someone like Eric
or
 Ron to jump in.>>

I don't offer an explanation. However, I have seen this often before. Many
years ago, Ron Oriti ( a meteorite collector and once head-guide at the
Griffith Observatory) purchased a Gibeon from, of all places, a rock shop in
Hollywood, California. I forget the weight but it was probably around 500
kilos. He sliced it like a loaf of bread, rendering slices perhaps 12-18
inches across. (I forget exactly as it was 30 years ago or more.) It was
not uncommon to see a discontinuity where apparently crystallization
proceeded from different regions with the Widmanstätten patterns oriented
differently, and approached an interface between them. Its not so much a
wedge, but rather a zone between the two areas where there is no pattern,
and this zone can be several cm. wide. As I have never possessed one of
these of my own (Oriti would never sell his old friend one as he wanted more
money than I could afford!) I couldn't pursue the interesting structuring
question. I however, have seen several of these slices, and I understand
that he still has a number left.

This is the best I can offer on this.

Ron Hartman

----- Original Message -----
From: Bernd Pauli HD <bernd.pauli_at_lehrer1.rz.uni-karlsruhe.de>
To: meteorite-list <meteorite-list_at_meteoritecentral.com>
Sent: Monday, March 18, 2002 11:31 AM
Subject: [meteorite-list] Deformed Gibeon patterns


> Anne wrote:
>
> > Vincent's Gibeon is amazing!
>
> Hello Anne and List,
>
> I agree and so is yours, Anne!
>
> > I picked up another odd one in Tucson. It looks as if it was made of
> > 3 different pieces: 2 have nice Widmanstatten patterns, but oriented
> > differently, and then there is wedge-shape piece with no pattern at
> > all. It is now on my site:
>
> > www.impactika.com/meteorites/gibeonslice.html
>
> > How do you explain that one?
>
> I wish I could and I have been waiting here for someone like Eric or
> Ron to jump in. Let's start with the easier part of the affair: the two
> Widmanstätten patterns which are oriented differently and that Gibeon
> slices are so famous for. They represent 2 original taenite grain bound-
> aries. A slice with a diameter of about 50 cm may show up to 9 different
> taenite grain boundaries and thus as many different orientations of the
> Widmanstätten pattern.
>
> As for this wedge-shape piece with no pattern at all, I can only guess
> that it is a severely heated, melted, and recrystallized inclusion or it
> might be a plessitic field.
>
> Best wishes and ...
> waiting for other
> list members' comments!
>
> Bernd
>
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Received on Mon 18 Mar 2002 04:10:08 PM PST