[meteorite-list] AD-L5 Polymict Breccia NWA 1697 and TAGISH LAKE

From: Matt Morgan <mmorgan_at_meteoritecentral.com>
Date: Thu Apr 22 10:18:24 2004
Message-ID: <3E3EEB53.282C738C_at_mhmeteorites.com>

This is a meteorite AD, delete if not interested.

I have a newly classified L5 polymict breccia to offer. Gary Huss
(Glenn's son) did the classification for me, the results of his work are

visible at the end of this email. The brecciation in this meteorite is
very nice and even better with slight magnification. It is only
slightly weathered, giving a weathering grade of W1, however it is
highly shocked (S4). All of the slices here were prepared to show some
brecciation. I did the best I could, and obviously, the larger the
surface area, the more clasts you will see.
    I am trying to keep the price per gram to the bare minimum, after
cutting and polishing about 25% of the stone was lost. Cost of the
slabs is $3.00/g and slightly lower on the 1 kg end piece. Total weight
is ~ 3 kg .Here is what I have to offer:
> 1000 gram end piece with fusion crusted back $2000.00 OBO
> 248 gram slice with crusted edge $744.00
> 233 gram slice with crusted edge $699.00
> 194 gram slice with crusted edge $582.00
> 178 gram slice with crusted edge $534.00
> 116 gram slice with crusted edge $348.00
> 107 gram slice with crusted edge $321.00
> 97 gram slice $291.00
> 67 gram slice $201.00
> 58 gram slice $174.00
> 38 gram slice $114.00

Images are at http://www.mhmeteorites.com/meteorites_for_sale.htm.
NOTE, the prices on my site are NOT DISCOUNTED!! Use the above price
tags.

Secondly, I placed many small mg sized fragments of the Tagish Lake
carbonaceous chondrite on my website for $2.00/mg. Many are very
affordable, so have a look!
http://www.mhmeteorites.com/meteorites_for_sale.htm

Thanks,
Matt Morgan

---------------------------------------------------
NWA 1697 CLassification by Gary Huss (ASU)
Classification: L5 polymict breccia, S4, W1

Description: The meteorite was received by Matt Morgan as a single
large fragment partially covered with black fusion crust. The sample
received by ASU for classification is a ~8 cm x ~5.5 cm slice. The
meteorite consists of a chondritic matrix with recognizable chondrules
enclosing many clasts of different types. These clasts range from black

fine-grained ones to chondritic inclusions. The slice appears to be
essentially unweathered. A thin section was prepared to include one of
the larger clasts.
The thin section shows minimal iron staining around metal grains and
the metal is only very slightly oxidized. The chondritic “groundmass”
is moderately recrystallized. Chondrules are still readily
identifiable, but the matrix is completely recrystallized and chondrule
boundaries are no longer clear. Porphyritic, barred, and radiating
chondrules are present in this section. Many of the olivines are
heavily fractured and show undulatory extinction. Mosaicism is evident
in many areas, and silicates are permeated with tiny metal and sulfide
particles (this made electron probe analysis particularly
challenging). A few chondrules still show twinned clinopyroxene. The
large clast in this thin section has similar characteristics, but seems
to be somewhat more recrystallized than the groundmass. In some areas
it is difficult to identify chondrules. The clast appears lighter than
the groundmass, primarily because the matrix is coarser grained. The
thin section did not include one of the dark clasts. The clast boundary

is recognizable, but is somewhat intergrown with the groundmass matrix.

Compositional Group: The olivines in this meteorite are essentially
homogeneous with a mean Fa value of 23.9±0.6 (PMD 2.3). The clast and
groundmass have the same composition (groundmass Fa 23.8±0.7 (n=8);
Clast Fa 24.1±0.2 (n=4)). The Fa and Fs values are solidly within the L

group.

Petrologic Type: Both groundmass and clasts are heavily
recrystallized., with indistinct chondrule outlines. There is minor
clinopyroxene and no large feldspars. These characteristics and
equilibrated olivines indicate type 5 for the groundmass and high type 5

or low type 6 for the large clast. The CaO content of the orthopyroxene

is low (~0.7±0.1; n = 5), consistent with type 3 or 4 chondrites, but
falling only marginally below the range for type 5 chondrites shown by
Scott et al. (1986). The textures and equilibrated olivines lead me to
a classification of type 5 breccia. The presence of non-chondritic dark

inclusions make this a polymict breccia.

Shock Classification: Most components of this meteorite have been
shocked. Undulatory extinction and heavy fracturing of olivines are the

rule. Some olivines show mosaicism, a few show planar fractures, and
many of the silicates contain tiny metal and sulfide grains, probably
due to shock. This indicates a shock level of at least S4. There is
also some evidence of post-shock annealing, so this object may have been

buried relatively deeply after the most severe shock event.

Weathering Classification: The near absence of silicate staining and
the very slight weathering of metal grains give a weathering grade of
W1.
Received on Mon 03 Feb 2003 05:21:07 PM PST