[meteorite-list] [AD]: NWA 8276 - the "NOT SO" ordinary chondrite L3.00/W1 (and the start of an interesting discussion?)

From: Mendy Ouzillou <ouzillou_at_meteoritecentral.com>
Date: Mon, 10 Mar 2014 12:34:44 -0700 (PDT)
Message-ID: <1394480084.30859.YahooMailNeo_at_web162602.mail.bf1.yahoo.com>

Hello everyone, The NWA desert continues to thrill us this with unique and amazing specimens. NWA 8276 is just such a meteorite. It is the second L3.00 and is "possibly" paired to NWA 7731. NWA 8276 features a rich, black crust and a yellowish matrix densely packed with chondrules. Extensive analysis by Dr. Carl Agee and Karen Ziegler support the 3.00 classification - a classification that indicates no heat or aqueous alteration of any kind (at least as far as can be presently evaluated). In fact, this meteorite represents material from the earliest history of our solar system. Older than CAIs? Not sure, but maybe Dr. Agee can chime in.

The complete writeup may be found here: http://www.lpi.usra.edu/meteor/metbull.php?sea=3.00&sfor=types&ants=&falls=&valids=&stype=contains&lrec=50&map=ge&browse=&country=All&srt=name&categ=All&mblist=All&rect=&phot=&snew=0&pnt=Normal%20table&code=59487

The
explanation how this meteorite was identified makes for a short but very good read (from MetBull):
"Adam Bates identified this meteorite from images he received as a possible pairing to NWA 7731,even though they came from a different Moroccan meteorite dealer. Both pieces were then purchased within a few weeks of each other in October 2013."

Adam Bates and I partnered on half the stone and anxiously awaited for Dr. Agee's results. It was not a given that this was in fact paired with NWA 7731, especially since the meteorite was bought from a completely different dealer. There were visual differences in the stone that led Carl to initially believe that 8276 may be different from 7731. In the end, the classification came back as L3.00 but with enough differences to state that NWA 8276 is "possibly" paired with NWA 7731. The terrestrial weathering is also
quite low and only an W1.

Many people state meteorites as being rare, but some are certainly rarer than others. The type 3.00 classification has only been given to 3 meteorites: Semarkona (LL3.00), NWA 7731 (L3.00) and now NWA 8276 (L3.00). Here is an excerpt from Dr. Agee's FB discussion with David Weir on the 3.00 classification and the rarity of this material:
"Grossman and Brearley (2005)define the subtypes less than 3.2 as 3.15, 3.10, 3.05, and 3.00. [This scale is] primarily based on the mean value and standard deviation of Cr2O3 in coarse ferroan chondrule olivines. I'm not saying that the Grossman and Brearley scheme is the ultimate, but it is simply the standard currently. What will really improve the subtype 3 nomenclature (and understanding of unequilibrated OCs) are more samples like NWA 7731 and NWA 8276. Up to now we have so few in the 3.15-3.00 range that the statistics of small numbers makes it hard to have meaningful subdivisions. I would gladly use an even finer scale (i.e. 3.01, 3.02, 3.03, 3.04 etc.) if it were actually established. The Grossman and Brearley (2005) scale is the only one that exists with any sort of sampling to anchor it. We just have too few samples to establish a finer scale. And when one starts talking about all the possible subtle differences around 3.00, I'm not sure if a
 numerical, linear scale would even make sense. The nice thing about discovering more of these very low type 3s is that more??will hopefully be available for research. Semarkona, because much of it??resides in India and some at the Smithsonian (I believe), it is hard to get a hold of. For example we only have a couple thin sections of Semarkona at UNM -- not even a tiny fragment!"


The items for sale (and pricing) may be viewed at http://www.meteoritesusa.com/meteorites-for-sale-4/nwa-8276-l3-00-w1-a-remarkable-and-scientifically-important-meteorite/


The photos have had no color manipulation and represent the true colors of this meteorite as viewed under studio lighting (5500K). Anyone interested in acquiring material may contact me by responding privately to this email or to Adam Bates (sales at bcmeteorites.com). The transaction and any associated details will be kept strictly confidential.?


Regards,

Mendy Ouzillou??
Received on Mon 10 Mar 2014 03:34:44 PM PDT