[meteorite-list] Semarkona - type specimen? (Clarification)

From: Michael L Blood <mlblood_at_meteoritecentral.com>
Date: Thu Apr 22 10:25:37 2004
Message-ID: <BAE00BEA.6690%mlblood_at_cox.net>

on 5/8/03 9:18 AM, pkmorgan_at_rmci.net at pkmorgan@rmci.net wrote:
> I would like to clarify that I was in no way questioning the integrity of
> Michael or how the specimen was represented. I believe at least one NWA
> (505 I think) had been recently "reclassified" and was wondering if the .0
> classification stuck to this one.
> Phil
---------
Thanks Phil & "Hi" to all,
        Dr. Rhian Jones is the one who classified Semarkona and is
the world expert in this field. In addition, NWA 1756 plots
tighter than Semarkona, making it even more pristine (see Adam's
post, below and connecting URL to the graph, which shows
the plotting 1756, 505 and Semarkona). As a result, the LL3.0
status of NWA 1756 would appear to be secure even if attachments
to Semarkona do pull on some heart strings.
        If list members are interested photos of a thin end piece of
this extremely rare material (there are only 68 grams TKW)
it can be seen at:

http://community.webshots.com/album/72441797VFLdiI

    List members will undoubtedly enjoy seeing this material in two
different photos taken in different lighting.
    Best wishes, Michael
PS: Anyone interested in this piece can contact me off list.

-----
Dear Phil and List Members,

The working name for the meteorite you are referring to is H178E. The
provisional name NWA 1756 has been assigned. The institution that studied
this meteorite submitted supporting data to the NomCom that shows this to be
an LL3.0. Dr. Rhian Jones, an expert on Semarkona was consulted. She
advised the laboratory that by comparing the Cr concentrations in type 1A
chondrules with Semarkona that an excellent case could be drawn in support
of the LL3.0 classification. Cr is very sensitive to metamorphism and is
lost very quickly so it is very diagnostic in determining low petrologic
grades.

For your viewing pleasure here is a link showing various plots of
unmetamorphosed ordinary chondrites. Note that NWA 1756 has the tightest
grouping in the plot indicating a pristine LL3.0 petrologic grade! We know
of no other ordinary chondrite that has shown such a tight grouping. We did
not mention the meteorite names of the LL3.3 and above because we felt this
information was unnecessary and may cause problems.

Plot Link:

http://www.lunarrock.com/nwa1756/nwa1756.jpg


This is just one of many charts created for NWA 1756. We do not want to
share everything at his time the scientist worked so hard to create. A
great amount of lab time and study was spent on this meteorite. A pristine
meteorite is not taken lightly and this may be why the NomCom is taking its
time considering the presented data before voting. It seems everybody is a
little impatient these days but serious meteorites require serious thought.

We hope this clears things up a little bit.

Best Wishes,

Adam and Greg Hupe
IMCA 2185


        
Received on Thu 08 May 2003 04:28:10 PM PDT