John,
Congrats on this new meteorite. I saw your eBay listing yesterday and was
initially surprised it was listed as a meso since it looks very much like some
of my fave meteorites, NWA 6392 & 6290, a brecciated diogenite. You can see
pics here: http://www.lpi.usra.edu/meteor/get_original_photo.php?recno=5656061,
http://www.lpi.usra.edu/meteor/get_original_photo.php?recno=5658147
Coincidentally, I also was reading the section just last night in Norton's
Cambridge Encyclopedia of Meteorites about the link between mesosiderites and
the HED group.
Mendy
-Original Message-
From: meteorite-list-boun...@meteoritecentral.com
[mailto:meteorite-list-boun...@meteoritecentral.com] On Behalf Of John higgins
Sent: Sunday, April 15, 2012 5:46 AM
To: meteorite-list@meteoritecentral.com
Subject: [meteorite-list] Introducing a spectacular new Mesosiderite Meteorite
NWA 6953 -AD
Dear Meteorite List,
I would like to take this opportunity to present to the scientific world and
collecting community at large a very exciting Mesosiderite meteorite.
Northwest Africa 6953 is an interesting new mesosiderite whose unique nature is
a result of its composition and the collective effects of long-term terrestrial
weathering. The metal content in NWA 6953 has experienced dramatic alteration
and has almost entirely been replaced with the iron oxyhydroxide goethite. But
it’s not the oxidation or alteration alone that makes this meteorite
fascinating. Studying how the iron oxidation process takes place on Earth in
NWA 6953, a predominantly orthopyroxene-rich meteorite, may have huge
implications for comparing how iron oxidation may take place in aqueous
environments on other alien worlds. (See BBC News article Spirit claims Mars
water prize http://news.bbc.co.uk/2/hi/science/nature/4094437.stm) More
importantly, studying this meteorite can potentially reveal clues as what to
look for in discovering other highly terrestrialized meteorites that until now
have mostly gone unnoticed.
This meteorite probably fell 40-50 thousand years ago when the Saharan desert
was sub-tropical. It was not a desert then, and the area experienced rainfall
much like any other place on Earth. NWA 6953 was exposed to a much wetter
environment, and after many millennia of weathering (at the surface and even
during burial and exhumation) nearly all the metal has been replaced with
terrestrial minerals. In fact, the visual appearance of the meteorite has been
radically changed into a strange and beautiful form that is unlike any other in
terms of aesthetics and chemistry. Voids in the meteorite matrix have been
filled with terrestrial minerals in crystal form, producing a prismatic effect
with internal reflections.
The visual similarities of this meteorite to a weathered orthopyroxenitic
diogenite gives some casual credence to the theory that asteroid 4 Vesta may be
the parent body of mesosiderites, and when the classification results came back
as a mesosiderite, everyone involved was quite surprised. The original metal
content (estimated to be about 30-40% by volume) has been replaced by
carbonates and goethite. However, the original orthopyroxene, calcic
plagioclase, minor olivine and some troilite remain, and even a few rare grains
of the original taenite and kamacite have survived. The refractive quality of
the crystal mixture is amazing, and another quality of this meteorite is the
presence of water trapped within the matrix during the terrestrialization of
iron hydroxides. (See the thin-section photos provided courtesy Mirko Graul
Meteorites)
As the newest and strangest member of the mesosiderite family, NWA 6953 is sure
to be the subject of much discussion and interest.
You can find the available offerings on my e-bay sales webpage
www.OUTERSPACEROCKS.com
or
http://stores.ebay.com/Outer-Space-Rocks
Currently I have 11 polished fragments up for sale, 7 buy it now and 4 auctions
currently at .99 More is available for purchase and trade, I also set aside a
significant portion of the find for the scientific community please inquire and
be free to ask questions.
Thank you and have a wonderful day!
Sincerely with best regards,
John Higgins
IMCA#9822
www.OuterSpaceRocks.com
email: geohigg...@yahoo.com
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