[meteorite-list] nwa869

From: Frank Prochaska <fprochas_at_meteoritecentral.com>
Date: Thu Apr 22 10:00:05 2004
Message-ID: <NDBBICFKNKHAAEEJLDALKEAPDBAA.fprochas_at_premier1.net>

Hello list,

Walter makes some key points here, and it should be pointed out that the NWA
situation is not unique in these problems. (Ironic that we refer to finding
so many meteorites in such a short time by so many people that we can't keep
accurate track of them all as a "problem.") NWA is just such a large
region, lacking named features even if people would tell us where exactly
all the pieces were found, and worked by so many people, the difficulties
are magnified.

For example, the reason we have Wellman a, Wellman b, etc., and Pampa a,
Pampa b, etc., is that it is not uncommon to find distinct meteorites within
another's strewn field. Nuevo Mercurio (b) was originally probably just
considered by it's finder to be another Nuevo Mercurio ordinary chondrite.
It later turned out to be a urelite. Roosevelt County in New Mexico is a
prime example of small scale version of what's happening in NWA, with the
advantage that more accurate locations of finds have come from Roosevelt
County than NWA, which helps sort out pairings. Look at the other stones
coming out of the Gold Basin strewnfield. Calcalong Creek was thought to be
just another Millibillille by the person who originally picked it up off the
ground, and David New had found other new meteorites in batches sent to him
from older finds from Austrailia, though at the moment I don't remember
which ones.

Another problem is testing a representative sample size. In very coase
grained breccias, you might need to slice a fairly large sample to see a
different variety of clast. Glorieta Mtn can be a beautiful pallasite, but
most of it looks like an ordinary iron, and I've seen pictures of sections
over 12" across with no hint of olivine. You don't necessarily know how big
a sample needs to be to be representative of the meteorite, unless you slice
up and sample the whole thing. You can pretty easily decide that the
original sample wasn't representative when something new is suddenly found
in an old fall though. It is difficult enough to get samples through the
labs these days at all, let alone with trying to send multiple samples of
what people believe to be one fall to a lab to try to err on the side of too
much material.

There may be something to the fact that they are coming out of NWA as well.
I would imagine if someone found a stone in Roosevelt County tomorrow, near
a known find or not, he or she would have a sample sent to a lab for pairing
or a new id. Perhaps with all the activity in NWA, and the fact that many
of these meteorites are not tested at all, a stone found similarly near a
known meteorite in NWA may be more likely attributed to another stone of the
same fall than a hypothetical new stone in Roosevelt County. That would be
hard for any of us to know for sure.

It appears to me from my casual observation of the literature and internet
reports that most every stone from Antarctica, unless obviously associated
with another stone by very close proximity, pieces fitting together, etc.,
eventually get their own analysis for id and pairing information.

The difficulties in id and pairings in NWA are not unique, though the size
and scope of the difficulties may be.

My thoughts on the topic . . . .

Frank Prochaska




-----Original Message-----
From: meteorite-list-admin_at_meteoritecentral.com
[mailto:meteorite-list-admin_at_meteoritecentral.com]On Behalf Of Walter
Branch
Sent: Sunday, July 07, 2002 5:43 PM
To: almitt; John Divelbiss
Cc: meteorite-list_at_meteoritecentral.com
Subject: Re: [meteorite-list] nwa869


Hi Al, John and List,

Al alluded to something which I would like to expand on and which I think
may be a source for at least some of the problems associated with multiple
pairings and classifications.

Let's take a certain strewn field, a geographical location where meteorites
have been found and continue to be found (okay, I admit - I am thinking of
NWA). Multiple individuals are finding meteorites. Finder A may find x
number of stones, then Finder B etc. and they are being sold to dealers J, K
and L. Any given number of resellers get involved. Eventually the
individual collector ends up with a given individual, slice, or fragment.
All along this path, a given stone has had the opportunity to be typed and
assigned a "real" number or name by the NomCom committee or given a
"temporary" number by someone, then perhaps classed by researchers, perhaps
with a number or name change.

To be honest, I am surprised that more confusion does not exist with regard
to pairings and perhaps it is a testament that there are not many such
instances that the system "works." Perhaps.

-Walter



-----------------------------------------------
Walter Branch, Ph.D.
Branch Meteorites
322 Stephenson Ave., Suite B
Savannah, GA 31405 USA
www.branchmeteorites.com
----- Original Message -----
From: "almitt" <almitt_at_kconline.com>
To: "John Divelbiss" <j.divelbiss_at_worldnet.att.net>
Cc: "Matteo Chinellato" <mcomemeteorite2000_at_yahoo.it>; "dean bessey"
<deanbessey_at_hotmail.com>; <meteorite-list@meteoritecentral.com>
Sent: Sunday, July 07, 2002 9:45 PM
Subject: Re: [meteorite-list] nwa869


> Hi John,
>
> I don't think your post should offend anyone and in my opinion is a very
relevant
> question and I wish more people would post along such lines. Until we
learn about
> something then we have to ask questions and anyone putting another person
down for
> asking a GOOD question along these lines forgets they at one time didn't
know the
> answer to the question either! The true nature of science is to ask
questions and see
> if something has been addressed or not.
>
> My hopes are that you will continue to ask and good threads as this one
continue on
> for those wanting to learn. I myself have to be humble with the many
gifted, and
> knowledgeable people on the list. Hopefully we will always have someone
that will be
> able to address an issue.
>
> Two good books that help out enormously are "The Cambridge Encyclopedia Of
Meteorites"
> by O. Richard Norton. I am just getting into reading my copy and can see
from what I
> have read and what I have check out, is a wealth of information contain
in this book.
> You are doing yourself an injustice by not having a copy. I am seriously
thinking of
> buying another copy to make sure I am never without it. It is proving to
be another
> fantastic book by Norton. Certainly a work of art more than a book with
information.
> One other book that I always like to recommend is Meteorites and their
Parent Planets
> by Harry McSween Jr. This book gets down into the nitty gritty of
meteorites also and
> helps with the understanding of classification and possible parent bodies.
>
> --AL Mitterling
>
>
> ______________________________________________
> Meteorite-list mailing list
> Meteorite-list_at_meteoritecentral.com
> http://www.pairlist.net/mailman/listinfo/meteorite-list
>


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Received on Mon 08 Jul 2002 12:56:51 AM PDT