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

From: bernd.pauli_at_paulinet.de <bernd.pauli_at_meteoritecentral.com>
Date: Sat Oct 1 11:40:16 2005
Message-ID: <DIIE.0000003000003D5C_at_paulinet.de>

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
Received on Sat 01 Oct 2005 11:40:14 AM PDT