[meteorite-list] Pairing discussion/questions

[Zelimir Gabelica]

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
Université 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