[meteorite-list] Info on Sikhote Alin's shrapnel

From: Jason Utas <meteoritekid_at_meteoritecentral.com>
Date: Tue, 17 Nov 2009 15:53:15 -0800
Message-ID: <93aaac890911171553m7c5e4108w83748b0006c2c519_at_mail.gmail.com>

Maurizio, Graham, Jeff, Fred, Darren, All,
I think Darren's hit on the fact of it - as I noted in my original post:

"Many batches of shrapnel do appear to be somewhat ablated due to the
method by which they have been cleaned (tumbling with ball bearings
tends to wear corners down and gives the false impression of surfaces
having melted)."

I think this is what you're noting, Fred - if you'd care to send some
pictures I'd be more than glad to have a look, but I'm fairly certain
that what you're seeing are mere remnants of the cleaning process.
Which isn't to say that shrapnel can't exhibit folded over rims, etc,
but such features are morphologically distinct from roll-over lipping
that we see in fusion crusts; it's one thing to fold a torn edge over,
and another matter entirely to force molten material over an edge to
form a lip.
I can't comment on the other features you've noted without seeing
pictures, but I would note that many Sikhotes exhibit crater-like
features that formed due to spallation caused by rust, which could
also be mistaken for bubbling.
I have only ever seen true bubbles on one Sikhote (and it is the only
*iron* meteorite that I've ever seen that actually showed true
bubbles) in my entire life; here's a photo.

http://www.flickr.com/photos/cameteoritefinder/2335708513/sizes/l/

Regards,
Jason

On Tue, Nov 17, 2009 at 12:08 PM, <debfred at att.net> wrote:
> ?Darren, I just looked at 119 individual pieces of shrapnel fragments under a microscope. They are rather small and range in size from 30 grams to less than one gram. It looks to me that every one of them shows some feature of melting. many have roll over rims, melted grooves, fusion crust with impact pits, bubbly crust on backside of oriented pieces. I doubt that any of these features were produced by tumbling.
> Regards, Fred
> -------------- Original message ----------------------
> From: Darren Garrison <cynapse at charter.net>
>>
>> I was under the impression (read it somewhere) that most modern=collected
>> Sikhote-Alin fragments are rusty and are cleaned in rock tumblers. ?If so, could
>> not that dull/round formerly sharp edges and make them look "melted"?
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Received on Tue 17 Nov 2009 06:53:15 PM PST