[meteorite-list] AD-Special: Premiere of a New Martian: - NWA 4925 - Olivine-orthopyroxene-phyric Shergottite

From: Martin Altmann <altmann_at_meteoritecentral.com>
Date: Sat, 5 Apr 2008 23:38:59 +0200
Message-ID: <019801c89765$75d3e050$177f2a59_at_name86d88d87e2>

Dear Collectors,

The presentation of a new Martian meteorite to the meteorite community is
always an event.
Such introductions of new lunaites and Martians are those moments that are
most fulfilling in the life and work of a meteorite-addicted person.
And we hope that you will share at least partially our exaltation about this
new fabulous stone, named

NWA 4925
Purchased 2007,
Morocco
Tkw 282.3g
o-SHE

Understandably, we aren't really unbiased regarding our new Mars rock, and
so we asked one of the best and most experienced connoisseurs of Martian
meteorites, Norbert Classen, known also to be the author of one of the best
homepages for lunar and Martian meteorites (http://www.meteoris.de/) for his
opinion on NWA 4295, and we are much obliged that he allowed us to report
his observations and his opinions about the new material:

"Right now we know about 50 different, i.e. unpaired Martian meteorites,
including 4 witnessed falls (Chassigny, Shergotty, Nakhla, and Zagami), 15
Antarctic finds, and 31 hot desert finds, most of them having been recovered
from the deserts of Africa. The majority of all Martian meteorites belongs
to the class of mostly "enriched" basaltic shergottites, while the
"depleted" group of olivine-phyric, and olivine-orthopyroxene-phyric
shergottites are far less abundant. NWA 4925 belongs to the latter subgroup
which consists of just about 5 different members, including the Dar al Gani
shergottites, NWA 1195, NWA 2626, NWA 2046, and NWA 4527 (TKW 10g). NWA 4925
is possibly paired with the latter one, but up to this moment no studies
have been conducted to prove or disprove this suspicion that's only based on
a comparison of overall texture, and weathering grade.

Like NWA 1195 and NWA 4527, the new NWA 4925 exhibits a pronounced light
colored weathering rind, typical for desert finds with long terrestrial
residence ages. Olivine phenocrysts near to or within the weathering rind do
often show a bright red appearance, a sign that most of the iron within
these olivines has been oxidized in the terrestrial environment. Overall,
the matrix color within or near to the rind is more redish - reminding us of
the same process that gives Mars its red appearance although most of the
Martian rocks are originally of grey, or grey to green color. The interior
of NWA 4925 is actually dark green, with shock altered dark-brown olivine
phenocrysts set in a matrix of more fine grained greenish pyroxenes and dark
maskelynite, both bearing witness for the fact that the interior of the rock
is more or less pristine and fresh, just as if it left Mars only yesterday.
It's that interesting contrast of the more light-colored weathering rind
with its neat redish olivines, and the dark-green, very fresh interior that
makes NWA 4925 visually most attractive, and scientifically interesting
because it models the surface weathering on the Red Planet.

>From the samples of NWA 4925 that I could study I would further suspect that
the olivine and orthopyroxene phenocrysts show a preferred orientation like
in NWA 1195, and other ol-opx-phyric shergottites, something which is
indicative of magmatic flow prior to the cooling and solidification of the
sample. Other most interesting features are melt inclusions, and small
chromites that are enclosed into the large olivine phenocrysts. Overall, a
very interesting, and optically most attractive new Martian meteorite of a
rare class. A "must have" for any serious collector of planetary meteorites,
and rare achondrites."
 

Dear collectors,
For us the acquisition of this new Martian was combined with various
difficulties and we are glad and happy to have it finally in our very hands.
Therefore we simply decided against all advice and economical reason to
share our joy and to choose for this introductory & exclusive special

a price of 400$ per gram!

We hope for your understanding, that this offer will be limited for the
pieces pictured on the special-page and for all other orders too (in case
the special-specimens will be sold out) until Sunday next week; and that
afterwards we will have to adjust the price to the more general Martian
price-level.

And here is the beef:
 
http://www.chladnis-heirs.com/special-nwa4925.html


Enjoy!
Martin & Stefan

Chladni's Heirs
Munich - Berlin
Fine Meteorites for Science&Collectors
Received on Sat 05 Apr 2008 05:38:59 PM PDT