AW: [meteorite-list] Purple (or bluish green) in a (stone) meteorite

From: dellenit <dellenit_at_meteoritecentral.com>
Date: Sun Oct 2 06:51:39 2005
Message-ID: <000601c5c78c$22fb2380$9300a8c0_at_hari>

Hi,

just a few remarks (corrections) on this issue.
Ringwoodite is not found in the matrix of the chondrites, but in the shock
veins (and close to the shock veins) of the chondrites. Bernd is right that
is needs at least S4.
But is was also found in LL6 chondrites - especially in NWA 757.

Reference: A. Bischoff: DISCOVERY OF PURPLE-BLUE RINGWOODITE WITHIN SHOCK
VEINS OF AN LL6 ...
www.lpi.usra.edu/meetings/lpsc2002/pdf/1264.pdf

Anyway, so if you didn't find this bluish inclusion connected or inside the
melt vein - i suspect it not to be ringwoodite.

P.S. i am currently writing an article about ringwoodite (for a german
magazine)

best regards

Harald



-----Urspr?ngliche Nachricht-----
Von: meteorite-list-bounces_at_meteoritecentral.com
[mailto:meteorite-list-bounces_at_meteoritecentral.com]Im Auftrag von
bernd.pauli_at_paulinet.de
Gesendet: Saturday, October 01, 2005 8:40 AM
An: Meteorite-list_at_meteoritecentral.com
Betreff: [meteorite-list] Purple (or bluish green) in a (stone)
meteorite


Pete wrote (with his daughter's crayon :-)

> The consensus seems to be ringwoodite.

Hello Pete and List,

Maybe it is ringwoodite that you spotted and photographed
in your unclassified NWA. As for the blue/purple something
that I found in my NWA 1584 (LL5) slice, I don't expect it
to be ringwoodite as it is "only" shock level S2 but should
at least have a shock stage of S4 or higher for ringwoodite
to occur.

Well, the matrix of your specimen looks darker than the matrix
of my NWA 1584 piece so that it may be more severely shocked.

The color of ringwoodite aggregates can range from purple to blue
and even to colorless. So far ringwoodite has only been found in L6
chondrites -- in other words, your specimen should not have too many
(well-defined) chondrules. If it is rich in chondrules, there is only
a slim chance the blue aggregates are ringwoodite.

The reason why we find ringwoodite only in L6 chondrites that are highly
shocked is because it is only formed locally when the olivine experiences
shock in excess of 50 GPa*.

*Pressures are measured in gigapascals (Gpa); 1 Gpa = 10 kilobar (kbar).


Best regards,

Bernd

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Received on Sun 02 Oct 2005 04:01:53 PM PDT