[meteorite-list] Why does shock blacken meteorites?

From: E.L. Jones <jonee_at_meteoritecentral.com>
Date: Thu Apr 22 10:10:03 2004
Message-ID: <3E8E4A27.8090409_at_epix.net>

Hello Bob,

Someone has suggested that the matrix of Park Forest is an impact melt
and that coloration is likely due to the composition of the other body.
  Occasionally the shock is so strong that some of the olivine does a
phase shift in crystal form to a spinel structure. This high pressure
form of olivine is a mineral called Ringwoodite. These veins, in thin
translucent section, tend to have a subtle purple tint. Otherwise it
looks black and opaque in cross section.

Regards,
Elton

Bob King wrote:
> Hi list,
> After seeing some excellent photos of Park Forest now -- thanks
> especially to Matt Morgan and Adam Hupe for sharing images of their
> slices -- I'm struck by how black the shocked part of that meteorite is.
> You can even see the transition from unshocked to shocked in a
> boundary zone of breccia. I've also seen this dark shocking in other
> chondrites. Can someone explain what happens physically or
> chemically inside a meteorite to turn a light matrix black during the
> shock (impact) event?
> Thank you for your help.
> Bob
Received on Fri 04 Apr 2003 10:14:47 PM PST