[meteorite-list] Fw: Recognizing E-chondrites

From: Larry & Twink Monrad <larrytwinkmonrad_at_meteoritecentral.com>
Date: Mon, 21 Dec 2009 19:05:13 -0700
Message-ID: <7324DAD499CA4425A02286E7F3C20A71_at_DFZN8X81>

Bernd asked me to post this to the list.
Twink Monrad

 Hi Greg S., Jeff Gr., Rob M., and List,

 Hard to tell in hand sample if a cut slice or an individual is an E
chondrite
 but if the suspect is an EH3 / EL3 or an EH4 / EL4 with clearly discernible
 chondrules and if it is not too severely weathered, its chondrules will
look
 grayish-white (= enstatite). But this may also be true of Kakangari
chondrites
 (and quite a few others) although the chance to own/find a K-chondrite is
 extremely remote.

 Relatively weathered E-chondrites like Dean Bessey's NWA 305* (W3) may be
 a challenge in hand sample because its chondrules (and matrix . what little
matrix
 there is) look colorful but it is relatively easy when you look at thin
sections of such
 E-chondrites under a microscope in cross-polarized light: they look a
little bit . well,
 boring because they consist almost exclusively of enstatite and enstatite
(orthopyroxene)
 looks grayish-white. No beautiful, colorful interference colors, . just
grayish-white
 chondrules and mineral debris.

 I also have thin sections of Abee (EH4), Eagle (EL6) but, . same story.
Not very spectacular,
 not very colorful in cross-polarized light. Of course, "not very
spectacular" does not refer to their
 scientific importance but only to their aesthetic beauty, and, beauty, we
all know, lies in the eyes
 of the beholder(s).

 * I've uploaded a picture of my NWA 305 endcut and another of my NWA 305
thin section
 in cross-polarized light so that you should be able to view them by
tomorrow (if interested) in
 the online Encyclopedia of the Met.Bull.


 Season's greetings,

 Bernd
Received on Mon 21 Dec 2009 09:05:13 PM PST