[meteorite-list] What is more important in classification?

[Alan Rubin]

I always want a doubly-polished thin section to do classification of stony 
meteorites.  To determine the petrologic type of a chondrite, it is useful 
to gauge the degree of recrystallization (best done in transmitted light) 
and look for the size of plagioclase grains (which can be done in an SEM, 
BSE mode of an electron microprobe, and in reflected light, since 
plagioclase is a darker gray than olivine or pyroxene).  To assess the 
degree of weathering, reflected light is most useful.  The probe, of course, 
will give you the olivine, pyroxene, plagioclase, kamacite, etc. 
compositions.  But in general, in order to get a feel for a stony meteorite 
(in terms of shock, brecciation, recrystallization, abundance of matrix 
material, etc.), I want to be able to use the probe and see the rock in 
transmitted and reflected light.  I can also then probe interesting features 
that reveal themselves with the petrographic microscope.  I don't worry so 
much about the fuzzy line between classification and research.
Alan


Alan Rubin
Institute of Geophysics and Planetary Physics
University of California
3845 Slichter Hall
603 Charles Young Dr. E
Los Angeles, CA  90095-1567
phone: 310-825-3202
e-mail: aerubin at ucla.edu
website: http://cosmochemists.igpp.ucla.edu/Rubin.html


----- Original Message ----- 
From: "Jim Wooddell" <jim.wooddell at suddenlink.net>
To: <meteorite-list at meteoritecentral.com>
Sent: Monday, January 06, 2014 7:57 AM
Subject: [meteorite-list] What is more important in classification?


> Hi all!
>
> Just a few general questions...
>
> The involves a mount and a thin section.
>
> What is more important now-a-days in classification?  This mainly revolves 
> some questions I have that I am
> not sure how to ask...mainly to those that classify.
>
> If you have a million dollar Scanning Election Microscope and can probe 
> around and
> can determine classification from the geochem and BSE images, how
> important is it to see the transmitted and reflected features in a 
> petrographic microscope?
>
> I suppose my thoughts and questions are possibly in reference to new 
> technology vs. old
> technology....maybe not...but close and really deeper than just yes and no 
> answers.  Not that SEM's are new technology...just saying.
>
> I was told a while back you can not classify without both.  So Why???  Are 
> the SEM's not capable of doing what
> a petrographic microscope can do?
>
> Thanks!
>
> Jim
>
>
>
>
> -- 
> Jim Wooddell
> jim.wooddell at suddenlink.net
> http://pages.suddenlink.net/chondrule/
>
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