[meteorite-list] Some help with [Brenham] inclusions

From: bernd.pauli at paulinet.de <bernd.pauli_at_meteoritecentral.com>
Date: 21 Aug 2007 21:27:20 UT
Message-ID: <DIIE.0000009E00001D96_at_paulinet.de>

Mike wrote:

"a description of which inclusions and colors go with which elements."

Hello Mike and List,

Here is my take: The round or slightly oval inclusions are troilite (FeS),
an iron sulfide - in meteorites the Fe:S ratio is almost ideally 1:1, one
iron atom versus one sulphur atom.

The elongated, "skeletal", inclusion with that golden tint should be schreibersite
crystals - chemical formula (Fe, Ni)3P.

The silvery "lining" surrounding the troilite inclusions and also around these
elongated schreibersite crystal aggregates is swathing kamacite. That's what
meteoriticists call that thin rim that often surrounds troilite, schreibersite and
silicate inclusions. This kamacite (nickel-iron with less than 7.5% nickel) is
the first to form from taenite (nickel-iron with more than 25% nickel) during
the primary cooling phase.

Reference:

BUCHWALD V.F. (1975) Handbook of Iron Meteorites, Volume 1, pp. 88-89.

Best regards,

Bernd

P.S.: I've really enjoyed your and Ruben's Glorieta Expedition adventures
in METEORITE; May 2007, Vol. 13, No. 2, pp. 15-18. Absolutely worth
reading !
Received on Tue 21 Aug 2007 05:27:20 PM PDT