[meteorite-list] Pairing discussion/questions

From: Zelimir Gabelica <Zelimir.Gabelica_at_meteoritecentral.com>
Date: Mon, 18 Jan 2010 18:53:21 +0100
Message-ID: <201001181752.o0IHqqha002442_at_smtpmul2.univ-mulhouse.fr>

Thanks very much Jeff.,

Your answer arrived while my post was sent. By
all means it better explains the complicated
situation regarding pairings than my poor trials.

Zelimir


At 18:01 18/01/2010, Jeff Grossman wrote:
>I think I've answered this before, but again:
>
>Yes, it would be great if all meteorites that
>fell as a single shower (in a single field o'strewn) had a single name.
>
>When a meteorite is found in Kansas or Germany
>or Mexico, it's fairly easy to look in databases
>and catalogs and find all the possible pairings
>within, say, 50 km. If there are any of the
>correct class, then it's ofter a simple matter
>to compare the two meteorites and decide if they
>are paired. NomCom rules actually require that
>this is done, and if the probability of pairing
>is high, a new name will not be granted to the new specimen.
>
>When a new meteorite is found in, e.g., Oman or
>Libya or Antarctica, things get much
>harder. With hundreds of potential pairings
>commonly existing, it is often very difficult or
>even impossible to evaluate pairings. If the
>type is rare enough it might be easier, but even
>then the job can be burdensome on the classifier and the answer uncertain.
>Once two meteorites are given a single name,
>specimens become mixed up; it would be very hard
>to separate two meteorites that were wrongly
>given the same name. In light of all this, the
>NomCom has decided that there is little benefit
>to even trying to pair meteorites... names are
>cheap and analysts' time is valuable. Therefore,
>each specimen can and should be given a separate name.
>
> From time to time, a situation comes up where a
> very strong case can be made for pairing two
> meteorites from a dense collection
> area. Usually the motivation for doing so is
> money: the owners don't want to donate 20 g or
> 20% type specimens of each of 10 valuable
> specimens that are so obviously paired. In
> this case, if they can make an overwhelming
> case for pairing, including geographic
> information, then the NomCom can grant a single
> name to the multiple pieces. For NWA specimens,
> this is not supposed to happen. The lack of
> geographic information means that one can not
> be certain of any potential
> pairing. Therefore, the NomCom will not grant single names to multiple finds.
>
>Of course, superimposed on all of this NomCom
>policy is what collectors and dealers do by
>themselves, unsanctioned by the Meteoritical Society.
>Probably everybody knows of cases where somebody
>obtained a new specimen and labeled it as an
>existing meteorite from NWA or another dense
>collection region. In addition, when NWA and
>other meteorites are first classified, there
>often are multiple pieces lumped
>together. According to NomCom rules, these
>groupings are only allowed when all the pieces
>were picked up within a few m of each other or
>fit together, but there is no guarantee that this is the case.
>
>So that's the story. I hope this explains some things.
>
>Jeff
>
>On 2010-01-18 11:09 AM, Greg Catterton wrote:
>>I have often wondered and after some discussion
>>with others I wanted to get the community feeling on the issue of pairings.
>>
>>If a meteorite say NWA 1877 for example is out
>>there and more is recovered and verified to be
>>the same material from the same strewnfield,
>>should the new material share the NWA number and the TKW be updated?
>>I have noticed many pairings with NWA 1877 and many other meteorites.
>>Same material with different numbers and TKWs listed.
>>
>>Would it not be in the best interest to have
>>all the paired samples share on number? This
>>would surely cut the amount of NWA material by 1000 or more.
>>Why is this not done?
>>
>>What is the process for pairing material to share the NWA number?
>>Is it up to the dealer or the person who did testing?
>>
>>What affect would it have on value if something
>>with a listed TKW of 200g suddenly was paired
>>with the 3 other numbers assigned to the same
>>material and the TKW was pushed to 1kg or more?
>>Surely it would decrease as supply grew. Is this a concern for some?
>>
>>I am trying to better understand the
>>politics/red tape that goes with this area.
>>
>>Thanks, hope everyone is doing well.
>>
>>Greg C.
>>
>>
>>
>>
>>
>>
>>
>>
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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
>
>
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Prof. Zelimir Gabelica
Universit? de Haute Alsace
ENSCMu, Lab. GSEC,
3, Rue A. Werner,
F-68093 Mulhouse Cedex, France
Tel: +33 (0)3 89 33 68 94
Fax: +33 (0)3 89 33 68 15
Received on Mon 18 Jan 2010 12:53:21 PM PST