[meteorite-list] primitive Ureilite ?

[Matt Morgan]

John:
I am sure Adam will have something to add but here is a good description
of Ureilites
http://www.daviddarling.info/encyclopedia/U/ureilite.html

I always thought that all ureilites were "primitive".  So someone please
enlighten us!
Matt Morgan

-----Original Message-----
From: meteorite-list-bounces at meteoritecentral.com
[mailto:meteorite-list-bounces at meteoritecentral.com] On Behalf Of
j.divelbiss at att.net
Sent: Tuesday, September 28, 2004 10:51 AM
To: meteorite-list at meteoritecentral.com
Subject: [meteorite-list] primitive Ureilite ?


Hello all,

I was reading one of Adam's auctions this morning and noticed the word
primitive attached to the word Ureilite and began to wonder what was the
latest status on Ureilites being considered "primitive". I know the word
is used with primitive materials like Acapulcoites and Lodranites
because their age is suggested at the chondrite level of 4.5+ billion
years.

I believe this reference for Ureilites infers the involvement of
pre-solar or solar parts such as the diamonds versus a formation age of
4.5 billion years. Or maybe I'm wrong about that. At one time the
diamonds were thought to be shock/pressure related, but recently
Ureilites with low-shock values have been found that has scientists
thinking that the diamonds came from some other source. 

What is considered the formation age of Ureilites?  And does that age in
itself make them primitive, or does the parts/pieces make them
considered primitive?

Curious,

John/JD



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