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Re: Armored Chondrules?

At 02:43 PM 10/23/97 -0400, you wrote:
>
>   While putting a high polish recently on a slice of Clovis #1, which is
>an ordinary H3 chondrite, I looked at it with my Spenser stereoscopic micro-
>scope at 10x and saw what appeared to be armored chondrules. I had to get the
>phase angle right to see them, but it looked like most, if not all, of the
>chondrules has a shell of metal (Nickle-Iron) surrounding each chondrule. Is
>this interpretation correct, and if so why didn't I notice it in other
meteor-
>ite slices I have looked at with the same scope?
>
>GWG
>
>

"Armored" chondrules have been known for a long time, and were noted 
first, I think, by Tschermak (1885).  They are not particularly 
well understood, but may be formed early in solar system history, 
during the original high-temperature event that melted the original
chondrule.  Metal may segregate from the silicate melt, and migrate
to the surface if the chondrule is spinning.  Just how it would
spread across the surface is a mystery.  Alternatively, a chondrule
might accrete metal-rich dust, and experience a second, light melting 
event.  

Some H chondrites seem to have more than their fair share of armored 
chondrules, probably because they have more metal than L or LL chondrites.

-Jeff Grossman