[meteorite-list] Classification Criteria was Am I missing something here?

From: Jeff Grossman <jgrossman_at_meteoritecentral.com>
Date: Sun, 22 Jun 2008 17:17:12 -0400
Message-ID: <OFD24CF771.2025F452-ON85257470.00751EFD_at_usgs.gov>

This question periodically comes up, and the answer is: there isn't one.

The fact of the matter is that there is no
"official" way of classifying meteorites (i.e.,
endorsed by a professional society or journal or
other group). When it comes to publishing
classifications, it is up to the authors and,
ultimately, editors to decide what to do.

The nearest thing to an "official" classification
is what you see in the Meteoritical
Bulletin. But this only looks official. Their
Nomenclature Committee's (nomcom's) primary
jurisdiction is only over meteorite names. Their
classifications are simply a matter of their own editorial policy.

The prevailing tradition on the nomcom is,
however, a sensible one. They normally publish
classifications that are consistent with common
usage among scientists. They are normally
conservative, meaning that they don't publish a
new type of classification until it is obvious
that at least a good part of the community has
bought into it. They also mostly do not publish
unusual classifications without reasonable
evidence to support it. They use the literature
as a guide to what criteria are necessary to
demonstrate a given classification. There is
usually enough expertise on the nomcom to do this
by inspection or with a little reading. However,
mistakes, oversights, and misjudgments can and do
happen in this system, especially at the fringes of "common usage."

As for the general scheme used, check out the
Wikipedia Meteorite Classification page, which I
largely
wrote.
http://en.wikipedia.org/wiki/Meteorite_classification.
For any given group, I may be able to give some
insight into what criteria the nomcom has
traditionally looked for. The two main
references cited there (numbers 2 and 3) are both
good classification papers that give a lot of
details on the properties of the various
groups. Unfortunately, both are chapters in
expensive books, but pdf reprints can probably be obtained from the authors.

Jeff





At 04:16 PM 6/22/2008, Mr EMan wrote:
>The geek in me has always been curious as to the
>actual classification criteria that a researcher
>uses to make classification. Does anyone have
>them by name or PDF or hard copy? Or volunteer
>to explain the general scheme for different
>classes? Sounds like fodder for a met-times
>expose??. Elton
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Dr. Jeffrey N. Grossman phone: (703) 648-6184
US Geological Survey fax: (703) 648-6383
954 National Center
Reston, VA 20192, USA
Received on Sun 22 Jun 2008 05:17:12 PM PDT