[meteorite-list] Ordinary chondrites - rarest to the most common classes

From: Martin Altmann <altmann_at_meteoritecentral.com>
Date: Thu, 17 Dec 2009 01:09:11 +0100
Message-ID: <000101ca7ead$93a77e30$07b22959_at_name86d88d87e2>

Hi Doug,

never I'd dare so. It was only an observation.
In former times there weren't 3.05 etc and as you know, we frequently give
type-3s in classification. Some classifier make decimal places, some not or
not yet.

Neither I had said something about the rareness.
And I fully agree about the pleasure to take a bath in as pristine
chondrules as thinkable.

My observation was a simple quantifying one.

No time, to harvest the database (I'm currently waiting to be on the road,
but due blizzards roads in half of the country of my destination are
closed).

But I suppose, that half of the type-3s weren't checked yet more detailed,
so that we can hope for more extremely unequilibrated ones!

(Especially if you keep in mind, that there is almost no meteorite with name
nor with an Antarctic number, which couldn't be rivalled by a hot desert
find, concerning the sole material).


Let it snow, let it snow, let it snow.
(But not exactly now!!)

Martin
  


-----Urspr?ngliche Nachricht-----
Von: Mexicodoug [mailto:mexicodoug at aim.com]
Gesendet: Mittwoch, 16. Dezember 2009 18:01
An: news at chladnis-heirs.com; Meteorite-list at meteoritecentral.com
Betreff: Re: [meteorite-list] Ordinary chondrites - rarest to the most
common classes

Martin wrote:
"Where one has to say, that it's maybe too early to say that, Because
the classification with decimal places, (even with two!), is a
relatively new occurrence..."

Dear Martin,

Your comment sounds to me like the hungry man's dubitable evaluations
of the quality of the the world's leading pancake expert, which
persisted until he ate his fill of her goodies.

Ref: "The Perfect Pancake" by Virginia Kahl http://tinyurl.com/ygjnju6

There are many parallels between say, beach combing and meteorite
collecting. While beauty is in the eye of the beholder and a thousand
and one contortions of the word "rarity" can and will be made by the
interested, I would personally say there is tendency of beachcombers to
want shells that are intact, whether it be for aesthetic reasons or
scientific study to best figure out everything from the evolution to
the habits of the mollusk who created his shell. The case is similar
with meteorites. Jeff's comment (as did mine) referred to the
scientific value of pristine examples which have not been cooked or
watered down. That is undeniable for those interested in the question
of genesis. Jeff and I have side-stepped the question of "rarity".
Personally I think it is moot here. If someone wants to study something
else like an LL3/LL4 smash up, or all the power to them regarding
"rarity" claims, since, like Semarkona LL3.00, only one of them appears
in the database.

Without considering Plutoing the R-chondrites, and with all respect
that each meteorite is unique in its own way, here?s the overview on
LL3 classification:

LL's are the rarest of the H-L-LL tribe (representing only 14%),
LL3 represents only 0.8% of OC's, the least frequent in the database.
Petrological grade 3's of any type (H-L-LL) are also the "rarest"
well-established classification - just 5%.

That would make LL3 a natural regarding "rarity", above and beyond its
scientific desirability to leading researchers like Jeff. Again the
words "holy grail" for OC's come to mind. The association of low
petrological grade (3) with scarcity for recovered meteorites is only
being extrapolated to the extreme with Semarkona, and is of very
arguably special scientific value:

Here?s the current LL3 situation in numbers:

Type # %LL's
LL3.X or LL3.XX 157 58.58%
LL3 102 38.06%
LL3-XX 8 2.99%
LL3/4 1 0.37%

To the point: As you can see, there is plenty more than a natural human
inclination towards perfection (with respect to raw sampling of the
unaltered first meteorites to condense from the soup) in the database
to argue that a LL3.00 or LL3.01 is hard to to find. I?m hopeful you
are right and more "most primitive" OC's are found as classification
gets more complex, but the tendency that many will be is just not there
if you look over the numbers so far covering (in this case) over half
of all LL3's.

If you want to say, for example, the "rarest" is the "H7"
classification - all nine of them- such as NWA 2898, I won't argue.
Many scientists have purposefully avoided that classification which is
another story. It just depends where your interests lie and all
meteorites have their unique story. I don't think we can look at this
as a bell curve with a 3 end and "7" end as the tails, though. If we
hypothesize that there is an OC-type origin point I hope we are having
a go at a singularity and elucidation of commonality In the
Beginning... I know, most of us would rather remain on the fence eating
all flavors of pancakes :-) ... it's such a loaded question ...
Kind wishes, and happy holidays
Doug


-----Original Message-----
From: Chladnis Heirs <news at chladnis-heirs.com>
To: Meteorite-list at meteoritecentral.com
Sent: Wed, Dec 16, 2009 8:27 am
Subject: Re: [meteorite-list] Ordinary chondrites - rarest to the most
common classes


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Received on Wed 16 Dec 2009 07:09:11 PM PST