[meteorite-list] RFS Picture of the Day: Wafer-thin slice ofTatahouine in Backlighting

From: bernd.pauli at paulinet.de <bernd.pauli_at_meteoritecentral.com>
Date: 03 Oct 2007 20:40:39 UT
Message-ID: <DIIE.0000009100002048_at_paulinet.de>

Hello List,

Someone asked in a private mail: "What's mosaicism?"

Here's an excellent explanation by O.R. Norton - it can be
found in "Cambridge Encyclopedia of Meteorites", p. 344:

"A characteristic of a mineral crystal seen microscopically under
crossed polarizers in which extinction is not uniform but checkered
into a mosaic pattern due to small irregularities within the crystal.
This occurs when the crystal has been distorted by shock metamorphism.
Mosaicism is an indicator of shock effects produced by an impacting
body."

I am glad someone asked this question as it may be the answer to my
own question about those dark bands in Tatahouine: "Does anybody
have any information about the nature of the dark bands that are visible
not only in this backlit specimen but usually in all Tatahouine specimens?
Shock darkening?"

Best wishes,

Bernd
Received on Wed 03 Oct 2007 04:40:39 PM PDT