[meteorite-list] On Stretch Tektites

From: Norm Lehrman <nlehrman_at_meteoritecentral.com>
Date: Fri, 2 Feb 2007 09:23:12 -0800 (PST)
Message-ID: <309410.13592.qm_at_web81003.mail.mud.yahoo.com>

Ma Lan & List,

"Stretch" tektites are specimens that partly broke and
bent after the skin had become brittle, but while the
interior was still semi-molten and taffy-like.

As commonly used, the term does not include
starburst-ray skin splits even though their
interpretation and significance is essentially
identical. To fit common usage, a stretch tektite
involves a triangular skin split associated with an
equivalent angular bend in the long axis of the
specimen. The material exposed within the split shows
a plastic, stretched character, like pulled taffy.

Nininger was first to publish on this subject,
describing two bent teardrops from Vietnam. They are
of special interest with respect to the debate on the
origins of skin pitting in Indochinites. Nininger
argued that the fact that the brittle part of the skin
shows pitting, but the stretched plastic part does not
(or very,very little), implies that the pitting
predated the skin split. Since the skin split
happened while the specimen was still mostly molten,
the ornamentation disrupted by the split must have
developed in the first few minutes of the tektite's
journey.

Conversely, the stretched part has experienced a few
minutes less exposure to soil acids than the brittle
skin. Say the brittle part is 780,000 years old.
That's about 409,968,000,000 minutes. The stretched
part is only about 409,967,999,995 minutes old. Could
that difference in length of exposure to soil acids
account for the observed difference in ornamentation?

I would guess the total number in collections as a few
dozen, but it is clear that they are more abundant
than that would suggest. Cookie and I have found four
good ones in the process of handling a few hundred
thousand tektites, so the abundance is on the order of
1 in 100,000.

I can't be sure about your specimen. In the photos I
don't see a bend in the overall specimen matching the
skin gaps. The gaps or "saw cuts" in some deeply
ornamented specimens are due to ablation or
terrestrial corrosion and do not involve plastic
skin-splits. Unless there is an angulation in the
specimen matching a triangular skin split, it is not a
stretch tektite per common usage of the term.

The most commonly confused tektite feature is what I
call the "starburst ray" skin split that results from
point impact while the specimen is still plastic
inside. The difference is purely semantic. But
ultimately, common usage dictates the definition of a
word, and by this, starburst rays are not "stretch
tektites".

There is a page on our website that discusses and
illustrates stretch tektites.

Cheers,
Norm
http://TektiteSource.com

 
--- Email from Chinaren76 <chinaren76 at yahoo.com>
wrote:

> Hi listees,
>
> On tektites, especially unusual tektites, for
> example,
> stretch tektites, i have several questions.
> 1. what's the definition of stretch tektites from
> the
> points of science?
> 2. How were the stretch tektites created?
> 3. How many are there the known stretch tektites
> found
> by meteorite/tektite collectors nowdays?
>
> In addition, i found one piece of tektite, with
> characteristics very similar to that of
> stretch-types,
> but i'm not sure. Please view photos from the link
> below:
>
> http://www.esnips.com/web/TektitefromChina
>
> 4. Is this piece a stretch one?
>
> Any tips will be deeply appreciated.
>
> Regards
>
> Miss Ma Lan
> Beijng, China
>
>
>
>
>
>
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Received on Fri 02 Feb 2007 12:23:12 PM PST