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

From: Jason Utas <meteoritekid_at_meteoritecentral.com>
Date: Tue, 17 Nov 2009 18:49:32 -0800
Message-ID: <93aaac890911171849y2608a737s409aff1ef6ca42d4_at_mail.gmail.com>

Hello Graham, All,
Well, there's always Albion, though that's quite a different beast. I
believe the druzy vugs found in that are accepted to be a product of
impact melting, as per Buchwald.
By the look of the specimen, I think it's safe to say that the bubbles
are the result of an accumulation of melt on the rear of a specimen
that maintained a stable flight for an extended period of time - much
as stony meteorites do, but for a longer period of time than is
commonly seen.
Here's a link to the first photo of the stone in my album:

http://www.flickr.com/photos/cameteoritefinder/2335700193/in/photostream/

To see the rest, just look at the pictures on the right and click on
the following photos..
Regards,
Jason

On Tue, Nov 17, 2009 at 5:10 PM, <ensoramanda at ntlworld.com> wrote:
> Amazing piece with bubbles Jason,
>
> Been trying to figure out how that could happen. It does not look like it happened due to melt during the fall but more like a feature from pre-entry, exposed after fragmenting.
>
> What are your thoughts...I can't think of any other irons with bubbles.
>
> Regards
>
> Graham
>
> ---- Jason Utas <meteoritekid at gmail.com> wrote:
>> 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 09:49:32 PM PST