[meteorite-list] Blue Bits in NWA 1584 Chondrules

From: bernd.pauli_at_paulinet.de <bernd.pauli_at_meteoritecentral.com>
Date: Sat Jan 29 08:14:06 2005
Message-ID: <DIIE.0000002C000031C4_at_paulinet.de>

Hello Darren and List,

> I was scanning some NWA 1584 slices (one of my favorite
> meteorites) and I noticed some iridescent-looking blue
> areas in some of the chondrules on one of them. I looked
> at the areas with a 20x hand lens and the blue is really
> there, ... anyone know what is causing this effect? The
> chondrules (if those are indeed chondrules) are around a
> centimeter across.

http://webpages.charter.net/garrison6328/bluebits1.jpg
http://webpages.charter.net/garrison6328/bluebits2.jpg
 
Yes, NWA 1584 is a beautiful, fresh LL5 chondrite -- this is
true at least for the specimens the Hupes offered some time ago.
Some other specimens that are being offered on EBay right now
look more severely weathered.

I have a very nice 10.8-gram crusted endcut from the Hupes and, here
is what it looks like: It has a grayish matrix with several clasts and
chondrules.

There is about 60% fresh black fusion crust showing polygonal contraction
cracks. A major feature is several large, mostly globular troilite aggregates
(up to 5 mm in longest dimension).

I looked for those ominous, bluish areas and I found some at high magnification
(32x and 56x), although they are not as conspicuous as yours. To me they have
a bluish/violet iridescent appearance and when I slowly rotate my specimen under
the microscope this iridescence appears and disappears periodically.

So it seems that this is (at least in my specimen) light reflected off
mineral grains (troilite, and, well, maybe chromite or ilmenite).

Darren, I'm going to attach three NWA 1584 JPEGs in separate mails to you
so that you see what I am talking about. One of these JPEGs shows a 5 mm
troilite inclusion (magnification 32x), #2 shows four of these violet/blue
things (magnification 32x) and another is a wide-angle pic of my specimen
(also showing this conspicuous 5 mm troilite inclusion at the upper left).


Best wishes,

Bernd
Received on Sat 29 Jan 2005 08:14:06 AM PST