[meteorite-list] Re: Sikhote Question, Impact Pits, Oriented Campo

From: Notkin <geoking_at_meteoritecentral.com>
Date: Sat Nov 5 21:12:23 2005
Message-ID: <bd1818b86e0134d713d44a09064df7ce_at_notkin.net>

Dear Jim, Matt, and Listees:

Jim, I enjoyed your good photo of that very unusual Sikhote, thanks,
and was interested in Matt's explanation.

Nice coincidence, as when you posted that I was about to photograph an
usual Sikhote-Alin of my own.

When I started collecting Sikhotes seven or eight years ago, I was
under the impression that all individuals had come through the
atmosphere on their own, and all shrapnel pieces were the result of
explosive fragmentation around the craters (this view supported, I
believe, by the fact that only shrapnel is found in the craters?). Over
time, I've seen a few pieces that exhibit characteristics of both
individuals *and* shrapnel, and I'm sure some of you have too. An
example would be, say, a ~1kg otherwise completely regmaglypted
individual that has one sheared, shrapnel-like face. I expect this is
the result of a larger individual fragmenting in the air shortly before
impact.

Now I've come across something really interesting: it appears to be a
normal shrapnel fragment, weight 266.4 grams, except it has a very
distinct impact pit and splash rim. It seems to me that an impact pit
could only have been formed during flight, meaning some "pure" shrapnel
pieces must therefore have been created by mid-air fragmentation, not
explosive fragmentation upon impact. Could such fragmentation be the
result of mid-air collisions, or breaking up along planes as a result
of atmospheric pressure?

Have a look:

http://www.aerolite.org/gallery/sikhote-alin-266-4.htm


Of course, this is probably all explained in Krinov's lovely little
book about Sikhote-Alin, but my Russian isn't up to it I'm afraid : )

Any comments, theories, or explanations welcomed.


And for those of you who -- like me -- dig impact pits, I have a lovely
little Sikhote with TWO impact pits closing on Ebay tomorrow, and a
gorgeous oriented regmaglypted Campo closing tonight in an hour. It's
at 12 cents per gram now! A real bargain for someone.

Here they are:

http://search.ebay.com/_W0QQfgtpZ1QQfrppZ25QQsassZpsiloceras


Best to all from Tucson,

Geoff N.
Received on Sat 05 Nov 2005 09:12:21 PM PST