[meteorite-list] Fw: Recognizing E-chondrites
Larry & Twink Monrad
larrytwinkmonrad at comcast.net
Mon Dec 21 21:05:13 EST 2009
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
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