[meteorite-list] Re: TEKTITES vs. Obsidian

From: EL Jones <jonee_at_meteoritecentral.com>
Date: Thu Apr 22 10:08:31 2004
Message-ID: <3D91ECBA.50407_at_epix.net>

Art, You asked how to tell the difference. One means is the probability
of overlapping distribution is very low. To my knowledge, unless there
had been trade activity amongst aboriginal Americans you should not
find Apache tears and tektites in the same area. The closest discovered
tektite occurrence is East Central Texas home of the bedisite variety.
Not to say they don't exist more eastward but SE New Mexico is the most
eastward occurrence of Apache tears I have seen. There was a rumor about
a tektite find in Northern Mexico but I think that was discredited. An
interesting side note is that georgiasites (central Georgia, USA) have
been found worked into tools by aboriginal craftsmen while not a single
bedisite has ever been found which had been worked --not bead, scraper,
knife nor arrowhead etc. Obsidian was a mainstay of tool making for
several tribes.

The differences are hard to describe and best obtained by experience.
Familiarize yourself with images of tektites and impact glass. One
great page is:
<http://home1.gte.net/res04m7h/mystery.html>

Most tears will of course be pebble shaped, usually smooth and are dark
or look like superficially like a "peach fuzz" sheen. "Raw" tears may
have concoidal dimples where stream tumbling breaks out a speck but are
usually smooth already depending on the distance they have been
transported. Both may be opaque to transparent. Some superficial
differences are:

Shape:
Tektites are predominantly flat, elongated, may have jagged protrusions.
Over all tends to be irregular and have very unequal axis( e.g. 2-4
times longer than wide or thick).
Tears are smooth and roundish as thick as they are wide. Tends to have
axies that are more equal (e.g. slightly oblong but the length is
usually no more than 1.5± times the width)
 Unbroken Surface:
Tektite: may appear: ropey, gritty, canaled, deeply gouged, twisted,
flight marked, ample crater-like depressions, bubbly, no metallic
sheen. can be dimpled like a golf ball. Internally, can have small bubbles.
 
Obsidian: Tends to be already uniformly smooth and dark--looks like
glass basically! Can be crazed under rough transport: as in having
star/ray shaped fractures of gray or silver covering most of the surface
or completely dark and uniformly smooth. This is ""BB" pellet against
the window pane" effect-- actually a reversed concoidal fracture but
there isn't any place for the fragment to go. Rarely has dimples. Never
bubbly and very rarely it have bubbles within. When bubbles are found in
volcanic glass they are usually the cavities left by mineral clusters
which have been leached out near a weathered surface and aren't gas
bubbles.

Luster:
Tektite is towards the greasy
Obsidian- remains dull but glasslike as in the surface of an old style
cola bottle which had been down the refill rack many times.

Surface- If translucent at all, a tektite will usually have an olive to
green to yellow tint to the basic gray or black color. Otherwise they
do look a lot like tears do. Tektites in thin slabs can have banding
like obsidian. However, the tektite banding will have a greenish tint
while obsidian has a black, red, or gold tint.

Of course there are exceptions to everything and the cut sections of
Tibetan tektites I've seen don't seem to have the green cast. I have
some australites that could be mistaken for tears on casually
observation were it not for telltale flight sculpting marks. Many
bedisites do have a shape closer to tears , but still have the jagged
irregular appearance.

An additional hobby of mine is natural glass and I've examined samples
from many areas of the world including impact, tektite, atomic, and
volcanic as well as for contrast slag glass and ancient man-made glass.
 I am fascinated by what is otherwise a mundane material. So common and
basic to our existance we rarely give it a thought, little alone as
much discussion as of late. I haven't seen a tumbled tektite but I'd
like to know what it would come out as. Perhaps others have tumbled some
and could discuss. There are some list members far more familiar with
tektites than I and whose works are published. There are vast amounts of
photos on the web, as well. and as I said in the beginning experience
is the best way to tell if you have an item which needs closer study.
 Photos do speak a thousand worlds and I am at my quota.

Regards,
Elton
 

thornysahuaro wrote:

<snip>

> If I'm out collecting Apache Tears and I should
>pick up a Tektite, how would I know the difference? If I happened to put
>that tektite into the tumbler with a batch of Apache Tears would there be
>any obvious differences when polished?
>Art Brasher
>
>
Received on Wed 25 Sep 2002 01:04:58 PM PDT