[meteorite-list] NWA 869...type(s): towards a solution ?

From: Zelimir Gabelica <Z.Gabelica_at_meteoritecentral.com>
Date: Thu Apr 22 10:22:39 2004
Message-ID: <1.5.4.32.20030616180711.0089ab6c_at_pop.univ-mulhouse.fr>

Hello list,

Regarding NWA 869/787 and their other paired friends, Dean Bessey recently
wrote that:=20
 "every institution that classifies NWA869 seems to get a different
classification".

This is actually true and probably debated in earlier posts.=20
If I am correct with my files, (but it is so easy to be fooled), NWA 869
seems to have been typed first as L4 (A. Rubin) then L5 (Met. Bull.).=20
NWA 787 (Farmer, Hup=E9...) was L6...
Matteo's NWA 900 (also described and pictured in Norton's Encyclopedia) and
supposed paired with the above, was suggested to be a L3.9-6 (Matteo) while
Norton writes about the same: "distinct chondrules and Fe-Ni clusters...
suggest L4" (?) "but there are also achondritic type materials in some=
 clasts".

I have a similar material in my collection and although it probably exhibits
quite the same (complex) lithology as the above, it was claimed by the
supplier to be first NWA 965, then recently corrected to NWA 905....I did
not find anywhere the description of this NWA 905..

Thus a lot of confusion concerning both the name and the type of this
exceptional meteorite! Not mentioning the total weight known or recovered
that stimulated recently a debate among the list.

To add to the confusion, Anne Black wrote this morning that the meteorite
"AC 001" she is offering on E-bay (found by Alain Carion in Morocco in 2000
and under study) has a quite unusual type LL3/5. This is probably not the
same meteorite as the above cited series except that my own "AC 001"
purchased last year in Ensisheim at AC's table, has a lithology that
strangely resembles that of my NWA 905, which should also be our famous NWA
869....

So far I am aware that this short statement throws even more confusion about
what is what and which type is which...
However, the purpose of this post is to tell you that by the end of this
week, during the newt Ensisheim show, we might have a good opportunity to
progress a little regarding the type of all these meteorites.

Pierre Rochette, a well known list member and pertinent contributor, who
recently published a new, rapid and efficient method allowing one to
determine the type of any meteorite (at least stony), kindly proposed to
help us determining the type of our unknowns (or doubtfull "knowns").=20
He will dispose of a special table during the next week held Ensisheim show,
for doing this fairly intriguing determination, thus by Friday June 20 only,
during the "professional day".
 Whoever would be able to bring along, among other unknowns, some NWA 869 or
alike for a "megnetic determination", this would perhaps throw some light on
our enigma.=20
At least, I'll bring along for that purpose my NWA 905 (3 different slices
with different lithoilogies each) and my two "AC001" pieces. Pierre and I
can make a short report on the results for the list after the show.

For those who are not familiar with this new method, here is the reference:
P. Rochette et al. (thus 7 other authors from France, Vatican, Italy, Spain
& Finland), MAPS 38(2), 251-268 (2003):
 "Magnetic classification of stony meteorites: 1 Ordinary chondrites"

The paper provides database of megnetic susceptibility measurements on 971
ordinary chondrites. This property can be sucessfully used to characterize
and classify OC type meteorites through a rapid and non destructuive
measurement essentially determining the amount of metal in each sample which
occurs in a very narrow range for each chondrite class.=20
In this compilation, Pierre et al. confirmed the majority of known types but
also proposed a new class for several meteoites, as different as (to take a
few sometimes represented in collections):
Kabo (was H4, now proposed L6)
Wiluna (was H5, now proposed L or weathering)
Albareto (was L4, now proposed L/LL4)
Suizhou (was L6, now proposed L/LL or weathering )
Ceniceros (was H3.7, now proposed L3.7)
Segowlie (was L6, now proposed LL6)
Futtehpur (was L6, now proposed H5)
etc. =20

Glad if anyone has comments about the method or about the NWA 869 or alike
puzzle.

Best to all,

Zelimir
******************************************************
Prof. Zelimir Gabelica
Groupe S=E9curit=E9 et Ecologie Chimiques (GSEC) - ENSCMu
3, rue A. Werner
F-68093 MULHOUSE Cedex, FRANCE
Tel: +33 (0)3 89 33 68 94
FAX: +33 (0)3 89 33 68 15
e-Mail: Z.Gabelica_at_uha.fr
******************************************************
Received on Mon 16 Jun 2003 02:07:11 PM PDT