Since Darryl brought up his incredible LL3.05, I have to ask how
does/can one classify the metamorphic grade to the to the tenths
or now the hundredths of a decimal? I have had some tell me this
is subjective and others say you need specialized equipment.
Please, any researchers, explain.
Darryl-
I don't mean to pick on your material, but it is a question that
has been nagging me for sometime and you stirred my brain!
Thanks in advance!
Matt
----------------------
Matt Morgan
Mile High Meteorites
http://www.mhmeteorites.com
P.O. Box 151293
Lakewood, CO 80215 USA
-----Original Message-----
From: Darryl Pitt <[email protected]>
Date: Wed, 16 Dec 2009 10:35:38
To: Jeff Grossman<[email protected]>
Cc: <[email protected]>
Subject: Re: [meteorite-list] Ordinary chondrites - rarest to the
most
common classes
Get ready for NWA 5717.....
Initially "anomalous," the classification had to be changed to
"ungrouped" as it was too difficult to determine what it was
anomalous
to. 3.05 subtype. More to follow....
On Dec 16, 2009, at 10:26 AM, Jeff Grossman wrote:
> At 09:27 AM 12/16/2009, Chladnis Heirs wrote:
>> Indeed,
>>
>> it's for the first time, that I read that R-chondrites are
included
>> in the
>> OC-group. If so, why exactly them and not the K-chondrites, the
>> Carbonaceous
>> from grade 3-6, the ungrouped and the enstatite chondrites too?
>
> I didn't say they ARE included in the OCs... I said that I thought
> they should be. As far as I know, I am alone in this opinion.
There
> are only two Kakangari-like chondrites, and I am not prepared to
put
> them anywhere. I'm not sure what the rest of the question means,
> but many ungrouped chondrites can be and are associated with a
major
> class, as in "ungrouped carbonaceous chondrite".
>
> jeff
>
>
>>
>> >valuable type of OC from a
>> >scientific perspective is petrologic type 3.00-3.01
>>
>> 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 - most classifiers seems still to
prefer
>> to use a
>> simple "3" - so that in case, there are still a lot known
type-3ers
>> awaiting
>> to be revisited regarding the degree of their (un)equilibration.
>>
>> But I agree - "Ordinary" is a somewhat misleading term,
>> - as the ordinary chondrites have told us most about the origin
and
>> formation of the solar system, the planets and ourselves, more
than
>> any iron
>> or any lunar rock!
>>
>> Keep that always in mind, if you are tempted, now in the end of
the
>> desert-era and the decreed end of meteorite finding in so many
>> countries,
>> with all their weird and fancy exotic types, to wrinkle your nose
>> about the
>> "ugly" ordinary 25$-a-kilo-chunk from NWA-wonderland!
>> Rare as brilliants they are - and they were our beginnings!
>>
>> Happy holidays to all!
>> Martin
>>
>>
>> -----Ursprüngliche Nachricht-----
>> Von: [email protected]
>> [mailto:[email protected]] Im Auftrag
von
>> Jeff
>> Grossman
>> Gesendet: Mittwoch, 16. Dezember 2009 11:33
>> An: Meteorite-list
>> Betreff: Re: [meteorite-list] Ordinary chondrites - rarest to the
>> most
>> common classes
>>
>> I agree with Doug... the rarest and most valuable type of OC
from a
>> scientific perspective is petrologic type 3.00-3.01, from any
of the
>> chemical groups. Only one is known... Semarkona. If we take a
more
>> expansive definition of "ordinary chondrite" than most of my
rather
>> conservative colleagues are normally willing to accept, I would
say
>> that
>> the rarest group of OCs is the R chondrites (only ~100 are
known and
>> many of those are paired). In addition, a number of unique
ungrouped
>> meteorites are OC-like. But again, I don't know of any
colleagues
>> who
>> agree with me that R chondrites are in the OC class. [I would say
>> that
>> the OC class has two clans, the H-L-LL clan and the R clan].
>>
>> Jeff
>>
>> Mexicodoug wrote:
>> > Hi Melanie and thanks for the enthusiasm you add to the
list ...
>> >
>> > Here's a high to low sorting of the "ordinary chondrites",
for over
>> > 32,000 meteorites:
>> >
>> > 22.0% L6 ("most common")
>> > 19.9% H5
>> > 12.9% L5
>> > 12.3% H4
>> > 11.5% H6
>> > 7.8% LL5
>> > 4.2% LL6
>> > 3.3% L4
>> > 2.2% H3
>> > 2.0% L3
>> > 0.8% LL4
>> > 0.8% LL3
>> > 0.1% L7
>> > 0.1% LL7
>> > 0.03% H7 ("least common")
>> >
>> > But this "common" and "rare" is a misleading label. That is a
>> harder
>> > question if you look too closely at the deails and consider
>> > inhomogeneous and brecciated ordinary chondrites. That can all
>> become
>> > somewhat unique if you ask the right person. Then there are the
>> motley
>> > crew of ungrouped ordinary chondrites where it is hard to
>> generalize.
>> > Some may be a weak classification while others might truly be
weird
>> > ("rare").
>> >
>> > Just a few notes: the H7, L7, LL7 types are not widely used
in the
>> > literature and border on impact melts, so I'd take them with a
>> grain
>> > of salt unless someone goes postal on me in which case they are
>> right
>> > in whatever they say. The way I listed these, the meteorites
are
>> > counted by the lowest number and won't show up in the higher
>> thermal
>> > (metamorphosed) levels. In other words, for example, an
LL3.8-6 is
>> > counted with the LL3's.
>> >
>> > If you have a special meteorite, it can sometimes be a "rarer"
>> type if
>> > you start to split hairs, like H3.8 instead of just grouping it
>> within
>> > the H3's, but there is some degree of arbitrariness to this.
The
>> > tendency is that more virgin Solar system stuff (closer and
closer
>> > 3.00) is more special and like a holy grail ("rare" in a
sense) to
>> > some who study that - since it is more representative of the
>> original
>> > material before water and heat were added and did their
thing. From
>> > hat we can try to get the proof we need to work out early
formation
>> > processes and theorize on the related dynamics happening. By
this
>> > logic, and considering it is a very studied meteorite, the
precious
>> > meteorite SEMARKONA (LL3.00 or is it 3.01 :-)), a witnessed
fall
>> from
>> > India, is rather unique being the only one with that 3.00
>> > classification, which makes it super intact since formation and
>> > especially interesting to experts, and most notably Dr. Jeff
>> Grossman
>> > who reviewed and updated its classification upon careful study.
>> >
>> > By another measure, the "common" ordinary chondrite, L5,
Canadian
>> > witnessed fall, VILNA, is one of those very few special
meteorites
>> > that was imaged during atmospheric entry and a precise orbit
was
>> > determined. It was not too far from Buzzard Coulee, and what
>> makes it
>> > even more special is that it was classified from a (although
>> witnesses
>> > heard pieces whizzing around) 94 milligram fragment with fusion
>> crust.
>> > The only other specimen found was a 48 milligram piece! This
>> becomes a
>> > wild anecdote of a meteorite tale when one considers that the
>> bolide
>> > passed directly over the only camera recording the sky for 500
>> miles
>> > (over 800 km) and headed for the newly constructed and
world's only
>> > UFO landing site which had been built for the Canadian
Centennial
>> > exposition in St. Paul, Alberta, where it showered sparks
>> > ("retro-rockets" to some folks). In case you wondered, I
believe
>> the
>> > Japanese classified on Antarctic meteorite with 10
milligrams, if
>> you
>> > can believe that!
>> >
>> > So what actually makes a meteorite rare can turn into a
matter of
>> > semantics and who you ask. Even the scale of 3 to 6 (or 7) is
>> somewhat
>> > arbitrary and just looks for convenient thermally changed
cairns
>> along
>> > the path toward melting. So if we went the other way, if H, L,
>> and LL
>> > correspond to only three parent bodies, the frequency of the
types
>> > follows:
>> >
>> > H 45.0%
>> > L 40.6%
>> > LL 14.3%
>> >
>> > Hope this helps a little with that general question!
>> >
>> > Kind wishes,
>> > Doug
>> >
>> >
>> >
>> >
>> >
>> >
>> >
>> >
>> >
>> >
>> >
>> >
>> >
>> >
>> >
>> > -----Original Message-----
>> > From: Melanie Matthews <[email protected]>
>> > To: [email protected]
>> > Sent: Tue, Dec 15, 2009 7:01 am
>> > Subject: [meteorite-list] Ordinary chondrites - rarest to the
most
>> > common classes
>> >
>> >
>> > G'mornin' listites,,
>> > What is the least common type of ordinary chondrite, as well
as the
>> > most common?
>> >
>> >
>> >
>> > Thanks
>> > -----------
>> > Melanie
>> > IMCA: 2975
>> > eBay: metmel2775
>> > Known on SkyRock Cafe as SpaceCollector09
>> >
>> > Unclassified meteorites are like a box of chocolates... you
never
>> know
>> > what
>> > you're gonna get!
>> >
>> >
>> >
>>
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>> >
>> >______________________________________________
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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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>> Meteorite-list mailing list
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>>
>>______________________________________________
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>> Meteorite-list mailing list
>> [email protected]
>> http://six.pairlist.net/mailman/listinfo/meteorite-list
>
> Dr. Jeffrey N. Grossman phone: (703) 648-6184
> US Geological Survey fax: (703) 648-6383
> 954 National Center
> Reston, VA 20192, USA
>
>
>______________________________________________
> http://www.meteoritecentral.com
> Meteorite-list mailing list
> [email protected]
> http://six.pairlist.net/mailman/listinfo/meteorite-list
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