[meteorite-list] D’Orbigny TS Follow-up

[MARK BOSTICK]

Hello all,

I thought I would recap D’Orbigny for the benefit of the group.

Re:. http://www.meteoritearticles.com/coldorbigneyts.html

I wrote.,

“One the best thin sections I have. OK, move over NWA 998, it is the best. 
This is due to its prismatic augite crystals, often found twisted with 
olivine, randomly placed anorthite shards, and the many large vugs/vug 
inclusions, in the stone. “

Augite is easy to see D’Orbigny.  Well it’s very easy to identify in all 
achondrites, athough at times looks a lot like pigeonite…at least to me.

In D’Orbigny, the augite grains have bunched together, creating as I noted, 
“prismatic augrite crystals”.  I will look over my achondrite thin sections 
later, but it seems to me that augrite usually does not bunch together such 
and the bright colors, usually more random.  Augrite never has appeared 
prismatic to my memory.

Anorthite shards are commonly found in achondrites as the mineral 
constitutes a lot of these meteorites.  They make me think of gray glass 
blades.  In polarized light, one half, going lengthwise, is usually a little 
darker then the other half.  Much like a how a blade of grass is lighter on 
the back side.  They also tend to have a strip leaf like appearance.

Olivine, like augrite in a thin section shows up in bright colors.  Augrite 
usually have more of a grain appearance, but in D’Orbigny, it is mostly in 
the prismatic crystals, and the two are easy to tell apart, in most cases.  
D’Orbigny augrite is usually found with olivine clumps.

All of the above is pretty basic and the easy to identify parts of 
D’Orbigny.

So onto the little red crystal, see in photo 7.

I wrote, “…perhaps it is olivine.”  My theory here was based on the note 
that much of the glass that filled some vugs, came from olivine and augrite. 
  And it appeared to be olivine over augrite.

Someone with much more knowledge then me noted it was, “Possibly apatite.”

And that the brown stuff seen in a couple of vug photos, “…likely to be 
carbonate..”.

On the subject of D'Orbigny TS's for sale, I only know of two sources.  
Marvin Killgore, who has some beautiful TS's, for around $1000 and Steve 
Arnold, Arkansas, who a person should e-mail if interested for details.  
This meteorite retailed for around $5000/g. when it came out.  The price on 
this meteorite has seemed to have gone done some.

Oscar Turone, of Meteorite.com, who has a museum on top of a mountain...and 
a meteorite mobile, is the person that first brought the meteorite to the 
market.

A small D'Orbigny part slice can be viewed on my web site:

http://www.meteoritearticles.com/coldorbigny.html

There are now nine augrites.  The new Maps will have an abstract or article, 
on the latest, NWA 1296.

Clear Skies,
Mark Bostick
Wichita.,Kansas
www.meteoritearticles.com