[meteorite-list] Ad - Rare Weekly Material Special

From: Adam Hupe <adamhupe_at_meteoritecentral.com>
Date: Thu Apr 22 10:27:44 2004
Message-ID: <04eb01c3a3b1$03cb4d60$d2dbe60c_at_attbi.com>

Dear List Members,

This weeks rare material special represents an outstanding benchmark
meteorite. As a matter of fact, we searched thousands of meteorites before
coming up with this one. We were lucky enough to acquire this stone while
looking at a nomad's offerings in the village of Safsaf a year ago. This
expedition was published in the February 2003 issue of Meteorite Magazine,
see cover story. This week we would like to introduce NWA 1756:

NWA 1756 LL3.0/3.2 Benchmark Meteorite

NWA 1756 is a primitive LL3.0/3.2, W1/2, S1 chondrite found October, 2002.
It may be the most pristine ordinary chondrite ever found with the possible
exception of Semarkona which is off limits to collectors. The reason we say
possible exception is that when comparing apples to apples and not apples to
oranges this meteorite plots cleaner than Semarkona (LL3.0, W0, S2)
according to one published method used for classifying low petrologic types.
Note in the chart below that every point for NWA 1756 is within the 3.0 box.
Also note that the red plot points (NWA 1756) are constrained to a much
smaller area than Semarkona in the diagram suggesting less metamorphism.

Petrologic chart link:
http://www.lunarrock.com/nwa1756/nwa1756.jpg

NWA 1756 was submitted as a pristine LL3.0 by two well-known scientists with
over 50 years combined experience in meteoritics. The chondrules where
carefully compared to those in Semarkona, were charted and were found to be
virtually identical. This represented an enormous undertaking by
scientists. As we understand it, the reason given for the LL3.0/3.2
petrologic range was that the published chart did not show the difference
between a 3.0 and a 3.2. If this given reason is correct, the argument does
not hold weight because if you look at the chart it assigns Semarkona a
perfect 3.0 yet NWA 1756 has a tighter plot meaning it is less metamorphosed
than Semarkona according to this published method. Adding to the problem is
that there are several systems in place to determine extremely low
petrologic types, which few seem to agree on. As we understand it, since
NWA 1756 has a weathering grade of W1/2 (lightly weathered) some of these
methods can not be used to accurately determine the petrologic type meaning
some other system will have to be used. We are not worried about this
because this stone will be studied in every conceivable way because of its
scientific importance. Also a few exceedingly rare minerals have been found
that do not exist in chondrites with the slightest degree of metamorphism.
It
is our belief that meteorites like this will help develop standards
furthering the knowledge of meteoritics.

What does this mean? We do not know because there are only a few meteorites
in the world that this can be compared to. Many scientists consider
Semarkona to be the most unequilibrated chondrite that exists, meaning NWA
1756 will be compared directly to it. We feel, when equal testing
procedures are performed, the well-studied Semarkona may be determined to be
less than pristine when equal standards are applied. After all, the 3.0
designation means perfect unequilibration and NWA 1756 shows no signs of
metamorphism and is not shocked with a rating of S1 compared to S2 for
Semarkona. Another issue is the xenoliths found in Semarkona, what
petrologic type are these, perhaps a 3.5? Does this mean that Semarkona is
really a LL3.0/3.5, W0, S2? Clearly, all these issues are open for debate
and it will be exciting to see the final outcome. We do not claim to be
scientists and are expressing our opinions, which are shared by those more
qualified than ourselves. We asked a lot of questions regarding NWA 1756 so
that we could hopefully present our views in a well-informed and accurate
manner. For your perusal we included the description found in the 88th
Meteoritical Bulletin below:


Northwest Africa 1756
Morocco
Found 2002
Ordinary chondrite (LL3.0/3.2)
A 68.2 g meteorite was purchased in Safsaf, October, 2002. Classification
and mineralogy (T. Bunch and J. Wittke, NAU): monomict chondritic breccia;
chondrules are very similar to equivalent chondrules in the LL3.0 Semarkona
chondrite in terms of phase/mesostasis compositions, zoning profiles, and
textures. Type IA olivine: FeO = 0.21 to 1.94 wt%; CaO = 0.31 to 0.51 wt%.
Type IIA olivine: FeO = 11.8 to 15.9 wt%; CaO = 0.10 to 0.19 wt%; P2O5 =
0.09 to 0.36 wt%; Chondrule mesostasis is optically isotropic. Matrix metal
is Ni-rich (50 to 60 wt%) and occurs in metal-pyrrhotite-haxonite ±
magnetite, chromite, carbon, cohenite, 0.1 to 0.2 mm aggregates; metal
contains small (<1 µm) SiO2-rich inclusions. Shock level, S1; one xenolith
is S4; weathering grade, W1/W2. Specimens: type specimen, 12.5 g and 2 thin
sections, NAU; main mass, Hupé.

Enough of the qualifications, this is one awesome meteorite that scarce few
collectors will be able to add to their collections. With 68.2 grams minus
two thin section cuts and a 12.5-gram type specimen there is very little to
go around. We will be donating a cleaner inner section to science for more
study further reducing the amount available. Who knows? This may become the
new benchmark in which all others are compared. This material is hundreds
of times rarer than planetary material and is priced according to weathering
grade associated with each prepared specimen, either a W1 (Very light
weathering) or a W2 (Light weathering). If you are considering
thin-sectioning and or scientific study we recommend a W1 specimen.

To look at these specimens check out our eBay auctions:

eBay Link:
http://members.ebay.com/aboutme/meteoritelab/

Thank you for looking and if you are bidding, good luck.

All the best,

Adam and Greg Hupe
The Hupe Collection
IMCA 2185
Received on Wed 05 Nov 2003 10:25:15 AM PST