[meteorite-list] Opinions on an oddball meteorite I cut open

From: Jason Utas <meteoritekid_at_meteoritecentral.com>
Date: Tue, 30 Jun 2009 21:03:00 -0700
Message-ID: <93aaac890906302103g8ec89bdr5ea765c19b7bfebd_at_mail.gmail.com>

>Eric wrote:

> The term "very low" when referring to magnetism in a stone meteorite is
> "very subjective" isn't it? Is there a scale to go by, or industry standard
> for strength of magnetism? I've had stone material that a super strong and
> very large neo magnet would barely stick to.

Everything's relative. It can be hard to judge L vs LL and sometimes
H vs L, but I would question the judgement of one who mistook an LL
for an H or vice-versa. Also, given the fact that the stone in
question appears to have experienced little-to-no internal oxidation,
and very little metal appears on the cut surface, again, I would
suggest an L or LL (probably LL) classification. You can attempt to
judge a meteorite's class by magnetic susceptibility, but I find that
weathering changes these results and makes the method rather
unreliable, especially as there is a wide overlap between the amount
of metal in LL's and L's, as well as between L's and H's.
Add weathering to this system and you just wind up with inaccuracies.

> Also wouldn't small slices such as this piece and others be hard to
> determine types due to the small mass.

Small meteorites are just as easy to classify as large ones, on
principle - to an extent.
So long as you have enough for a thin section, and maybe for analyzing
isotopes, an analysis is as easy as any other, at least insofar as you
don't need more material to classify a meteorite. But you seem to be
pointing towards asking whether or not the classification would be
accurate, due to heterogeneous breccias - see below.

>I mean, a small 10 gram stone
> wouldn't be completely representative of an entire mass if that mass is
> unknown would it?

You're addressing a different issue, and one that is...an impossible
one to address. What if every other meteorite ever found weren't a
representative sample of the body from whence it came? Look at the
paired Dhofar lunars that were only tied together when one stone
chanced to have all three lithologies present, or Seymchan - IIE vs
pallasite. Chergach IMB vs plain ordinary chondrite, and Park Forest
- ordinary L6 vs L-IMB. You work with what you have. If it's small,
you classify what you've got and hope more turns up. But you're
talking about NWA, so in all likelihood, 5kg already has come
overseas, and it was classified six months ago.

But that's science. If evidence comes forth and proves conclusively
that this stone is a clast out of an L4, then it will be deemed
paired. Until the stone is found that can prove that, it's a distinct
meteorite.

> I've seen and cut some chondrites with dual lithologies
> but if I cut those stones in half down the separation line of the mineral
> types, how would you know what type it is?

It would be the type you were left with, because that would be the
composition of the meteorite that was being analyzed.
You can only analyze what you have to work with...

Regards,
Jason

> Regards,
> Eric
>
>
>
> Jason Utas wrote:
>>
>> Hola,
>> Check out the last picture - there's a white chondrule clearly visible
>> in the upper right/center of the photo.
>> Also note the dark chondrule (large, but fuzzy) at the bottom edge of
>> the slice, a tad to the left of center.
>> I'd go with LL6; it has a few chondrules, and from what I understand,
>> the type seven designation is reserved for primitive achondrites. ?Of
>> course, it's hard to gauge L vs LL, but you did say that the magnetism
>> was "very low."
>> Regards,
>> Jason
>>
>> On Tue, Jun 30, 2009 at 2:11 PM, Galactic Stone &
>> Ironworks<meteoritemike at gmail.com> wrote:
>>
>>>
>>> Hi Listees!
>>>
>>> I'd like some opinions on a meteorite I cut open yesterday. ?It's an
>>> oddball I've had in my box of NWA for some time - awaiting a date with
>>> the saw. ?It exhibits a very low magnetism and it has a grey matrix
>>> almost entirely devoid of chondrules - although there does appear to
>>> be some remnant chondrule structures. ?I'm hoping it might be some
>>> kind of achondrite, but the magnetism mostly rules that out. ?Is it
>>> some uncommon type like an L7? ?Or is it just something common that I
>>> have not seen before?
>>>
>>> The exterior has a wind polished desert varnish on it and there
>>> doesn't appear to be any fusion crust to speak of - although there are
>>> a few scattered tiny patches of black on it. ?The stone weighs 16
>>> grams. ?I only made 2 cuts - I cut one corner off to expose the matrix
>>> (endcut) and I made one thin slice. ? The rest of the stone is intact.
>>>
>>> Here are some photo links -
>>>
>>>
>>> http://i268.photobucket.com/albums/jj24/Meteoritethrower/Meteorites/Anomalous/new-odd-cut/odd-new-1.jpg
>>>
>>>
>>> http://i268.photobucket.com/albums/jj24/Meteoritethrower/Meteorites/Anomalous/new-odd-cut/odd-new-2.jpg
>>>
>>>
>>> http://i268.photobucket.com/albums/jj24/Meteoritethrower/Meteorites/Anomalous/new-odd-cut/odd-new-3.jpg
>>>
>>> Any opinions are welcomed.
>>>
>>> Best regards,
>>>
>>> MikeG
>>>
>>> --
>>> .........................................................
>>> Michael Gilmer (Louisiana, USA)
>>> Member of the Meteoritical Society.
>>> Member of the Bayou Region Stargazers Network.
>>> Websites - http://www.galactic-stone.com and http://www.glassthrower.com
>>> ..........................................................
>>> ______________________________________________
>>> http://www.meteoritecentral.com
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>>>
>>
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>
>
> --
> Regards,
> Eric Wichman
> Meteorites USA
> http://www.meteoritesusa.com
> 904-236-5394
>
>
Received on Wed 01 Jul 2009 12:03:00 AM PDT