[meteorite-list] NWA 4024/2680

From: Zelimir Gabelica <Zelimir.Gabelica_at_meteoritecentral.com>
Date: Tue, 19 Jan 2010 15:46:29 +0100
Message-ID: <201001191446.o0JEk2uS018887_at_smtpmul2.univ-mulhouse.fr>

Hi Jason,

Excellent link for NWA 4024 compared to 2680 (Birdsell).
 From what I just can discern, I am convinced
2680 is exactly the same material as 4024.
See, as comparison, the pics of both meteorites
added at the end of their respective Met. Bull
reports (although NWA 2680 is still provisional, there are pics attached).
In particular Mirko Graul provided pics of both.
Here they are, for comparison:

NWA 2680:

http://tin.er.usgs.gov/meteor/get_original_photo.php?recno=5645813

and NWA 4024:

http://tin.er.usgs.gov/meteor/get_original_photo.php?recno=5645817

Very similar slices, almost same pattern (look at details!)

My modest suggestion:

Owing to the fact that NWA 2680 is still
provisional, why not suggesting to this specific
classification working team (Zolensky & al ?) to
conclude (after a thorough re-examination) that
both meteorites are the same and thus also
consider to maintain only one NWA number, thus
that NWA 2680 is identical to NWA 4024 (that
should have priority because first classified)?

But here the question is perhaps even more
complicated because NWA 4024 is said to be a
winonaite, while it now appears obvious that only
one (or a few) achondritic clast(s) were analyzed
in it, not the (major ?) iron found all around (that is IAB ungr.).
It would then be wise to fully re-analyze both
materials (ideally by the same team) and conclude.
If there rises evidence that both are the same,
then I guess there should come an agreement for a common type and name ?

Sorry, I am not in the Nom Com nor I know how
they would proceed in such a case, so perhaps my suggestion is very naive.
I therefore expect more comments from Nom Com
experts and am ready to humbly accept their conclusions whatever they be.

This is here only one typical example of
something that could still be done, because NWA 2680 is not yet official.
There are probably other such favorable examples.
Solving them, even if progressively, will push
the pairing problem one step forward, though it
is obvious, as Jeff pointed out, that this
pairing problem is really very difficult (I'd say
impossible) to solve completely.


Zelimir

At 12:56 19/01/2010, Jason Utas wrote:
>Hello John, Zelimir, All,
>I've held samples of both; NWA 4024 is indistinguishable from NWA 2680.
>
>http://www.arizonaskiesmeteorites.com/AZ_Skies_Links/NWA_2680/index.html
>
>http://www.meteoriteguy.com/catalog/nwa4024.htm
>
>It was likely misidentified the second time around because the sample
>sent in for analysis was too small for an accurate study - or perhaps
>the person who performed the analysis simply wasn't expecting an iron.
> Either way, it's funny - an analysis based solely on the study of a
>clast that comprises at most ~30-40% of the total volume of the
>meteorite...I've never seen that done before.
>It's a IAB with silicate inclusions - a pretty one, but an example
>that's not crazily different from a few already-known irons. Oh, and
>it has winonaite-type silicate inclusions. Just like Campo del Cielo
>and many other IAB's...it's pretty typical in that respect.
>We purchased a ~40g individual as a new iron in Tucson three or four
>years ago; there were hundreds of small individuals of this iron
>available at the time, totaling at least several kilograms (most
>weighed only a few grams; Dean Bessey sold some of them on ebay later
>that year, again, misidentified, and mixed with small mesosiderite
>fragments). In Tucson they were being sold as Zagora; we were
>surprised to find a very fine pattern after we removed an end from
>ours for analysis.
>Based on what I have seen personally, I would estimate the TKW of the
>find to be at least ten kilograms, but knowing NWA, there could be
>(and likely is) much, much more.
>Regards,
>Jason
>
>On Tue, Jan 19, 2010 at 2:58 AM, Zelimir Gabelica
><Zelimir.Gabelica at uha.fr> wrote:
> > Hi John,
> >
> > NWA 4024 is indeed a nice example of the
> discrepancy between Met. Bull. data
> > and the amount of stuff circulating on the market.
> >
> > This is perfectly illustrated if you compare the Met. Bull. write up
> > regarding NWA 4024 an look at the photos included at the end of the same
> > report.
> > There are some 15 pieces illustrated, coming from various sources. Although
> > weights are not mentioned, a rough evaluation of the volume of the pieces
> > (comparison with the scale cubes) leads to
> evaluate that the total weight of
> > the illustrated pieces should largely overstep 100 g, probably more.
> > Not mentioning that the pieces pictured probably represent only a small
> > fraction of what is really available as 'NWA 4024" in collections.
> >
> > I have in collection a 4.43 g end section (got from Hanno Strufe).
> > But my own write up states that Mike Farmer
> reported at the time (2006) that
> > the tkw was at least 745 grams.
> > He explicitly explained this discrepancy by the following argumentive
> > comment: "first piece sold, more pieces come
> out", which is, as we know, not
> > really a surprise.
> >
> > Nothing is mentioned officially about
> pairings and I don't know whether this
> > meteorite is also being sold under another NWA N? but I guess the pics in
> > the Met. Bull. suggest that all the 15 pieces were called "NWA 4024".
> >
> > The tkw of a meteorite is indeed rarely updated officially (by the Nom Com
> > and thus reported in the Met. Bulls.)
> probably because nobody writes them to
> > update the old tkw. I agree that the Nom Com should not be blamed for that.
> >
> > As a typical example (among many others) the official tkw reported in Met.
> > Bull. for Chiang Khan is still 367 grams,
> while everybody now agrees that it
> > is of several kg.
> > When helping Mike Jensen to update the 2008 edition of "Meteorites from A
> > to Z", I reported him several such examples and, in some obvious cases, the
> > actual tkw was updated (with, as reference: "numerous sources including
> > internet, personal communications and professional experience".
> > Needless to say that this updating is not official because not (yet ?)
> > agreed by the Nom. Com.
> > For the cited example of Chiang Khan, we
> agreed to the put, as tkw, 75+ at 7.0+
> > kg, which is more realistic regarding the present market, although not
> > official as I agree only the Met. Bull. (Nom. Com.) should act as official
> > reference.
> >
> > There is some pertinent work needed here and I am convinced many of us from
> > the List and elsewhere can help in trying to
> provide more correct figures to
> > the Nom. Com.
> >
> > Zelimir
> >
> >
> > At 04:38 19/01/2010, John.L.Cabassi wrote:
> >>
> >> G'Day List
> >> This has been a very interesting read. Quite some time ago, I brought up
> >> the question about NWA 4024, which apparently on the card that
> >> accompanied it and the Met Bull stated a TKW of 38.1g. But there's
> >> definitely alot more out there ??? Is there pairing going on here?
> >>
> >> http://tin.er.usgs.gov/meteor/metbull.php?sea=nwa&sfor=names&ants=&falls
> >> =&valids=&stype=contains&lrec=50&map=ge&browse=&country=All&srt=name&cat
> >> eg=Winonaites&mblist=All&rect=&phot=&snew=0&pnt=Normaltable&code=34296
> >>
> >>
> >> And now for another, I purchased this off of Tom some time back. NWA
> >> 231, the met bull lists is as being provisional, it has yet to be
> >> classified. The main mass was 1054g. What I have is 1048g, 6 grams are
> >> missing; I think due to polishing a window. But I confirmed with Michael
> >> C. and it was confirmed. The label on the rock states "NWA 231" so
> >> everything checks out. But it's yet to be classified. I have not found
> >> the time to go ahead with this, but I was curious that NWA numbers were
> >> handed out prior to being classified.
> >>
> >> http://tin.er.usgs.gov/meteor/metbull.php?sea=nwa+231&sfor=names&ants=&f
> >> alls=&valids=&stype=contains&lrec=50&map=ge&browse=&country=All&srt=name
> >> &categ=All&mblist=All&rect=&phot=&snew=0&pnt=Normaltable&code=31470
> >>
> >> Any thoughts?
> >>
> >> Cheers
> >> John
> >> IMCA # 2125
> >>
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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
> > ______________________________________________
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> >
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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 Tue 19 Jan 2010 09:46:29 AM PST