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 The original metal content (estimated to be about 30-40% by volume) has been replaced by carbonates and goethite.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.
OFFICIAL CLASSIFICATION DATA SOURCE:
The Meteoritical Society International Society for Meteoritics and Planetary Science Lunar and Planetary Institute Meteoritical Bulletin DatabaseNorthwest Africa 6953 | |||||||||||||||||||||||||||||||
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Basic information | Name: Northwest Africa 6953 This is an OFFICIAL meteorite name. Abbreviation: NWA 6953 Observed fall: No Year found: 2011 Country: (Northwest Africa) Mass: 4.16 kg | ||||||||||||||||||||||||||||||
Classification history: |
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Comments: | Approved 23 Apr 2012 | ||||||||||||||||||||||||||||||
Writeup | Writeup from MB 100: Northwest Africa 6953 (NWA 6953) (Northwest Africa) Purchased: Sept 2011 Classification: Mesosiderite Petrography: The primary metal in this specimen (originally ~30-40 vol.%) has been almost entirely altered by terrestrial weathering, with minor amounts of remnant kamacite and taenite. The other constituent minerals are orthopyroxene, very calcic plagioclase, and troilite. Geochemistry: Orthopyroxene (Fs24.9Wo2.5, Fs31.8Wo3.3, Fe/Mn=30), olivine (Fa37.6-37.9, Fe/Mn=46-47). | ||||||||||||||||||||||||||||||
Data from: MB100 Table 0 Line 0: |
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Institutions and collections | UWS : University of Washington, Department of Earth and Space Sciences, 70 Johnson Hall, Seattle, WA 98195, United States (institutional address; updated 15 Jan 2012) |
IMCA ( INTERNATIONAL METEORITE COLLECTORS ASSOCIATION ) I AM MEMBER # 9822 JOHN HIGGINS. THIS METEORITE IS FROM MY PERSONAL COLLECTION. I AM THE MAIN MASS HOLDER WITH NO BREAKS IN THE CHAIN OF PROVENANCE. MY NAME MATCHES THE ONE LISTED IN THE METEORITICAL SOCIETY BULLETIN OF WHICH I AM A LONGTIME MEMBER IN GOOD STANDING. I HAVE GONE THROUGH GREAT LENGTHS TO PERSONALLY PROCURE, CURATE, CUT, EXTENSIVELY POLISH AND PRESENT THIS METEORITE. THIS OFFICIALLY CLASSIFIED HIGH QUALITY METEORITE HAS CONTRIBUTED TO THE SCIENCE OF METEORITICS THROUGH RESEARCH LED BY THE WORLD RENOWN TEAM AT THE UNIVERSITY OF WASHINGTON, SEATTLE. GUARANTEED AUTHENTICITY The authenticity of this meteorite has a 100% guarantee. Signed Certificate of Authenticity Included. Comes with acrylic display case/box to protect and show your new meteorite. First class delivery and provenance provided exhibiting important details of the classification & petrography. 1cm scale cube for reference purposes. SHIPPING: Shipping and Delivery Usually $3.49 US and $12.75 International Includes postage costs, packaging & handling. International shipping may be subject to import duties or other taxes. I normally dispatch your order the following day after payment is completed (Mon-Sat).Your goods will be shipped from USA, if you live outside US, the Items normally take 7-14 days but please allow up to 20 days for delivery in case of postal delays. COMBINING SHIPMENTS: Please request a total combined invoice after you are done bidding on all items. Postage can vary when buying multiple items based upon weight, my goal is for each customer to pay the cost of postage, no more or less. CANADA: Shipping to you may be slightly cheaper than Global destinations, please request a total for single items. |
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