[meteorite-list] Obsidian that looks like Tektites

From: Robert Verish <bolidechaser_at_meteoritecentral.com>
Date: Thu Apr 22 10:06:53 2004
Message-ID: <20021001071359.38045.qmail_at_web80312.mail.yahoo.com>

Hello All,

Here is another California "apache tears" locality for
tektite-shaped "obsidianites" - Coso Mountains.

The following abstract appeared in "The Leonard
Memorial Issue" of Meteoritics (The Journal of the
Meteoritical Society) Volume 2, Number 1 - May 1963:

"Comparison of Surface Features of Tektites with
Surface Features of Natural, Chemically Etched
Obsidian found in the Vicinity of Coso Hot Springs,
Inyo County, California"

   by Lee F. Humiston and Richard T. Zbur

(Research Department, U.S. Naval Ordinance Test
Station, China Lake, California)

    Striking similarities have been found between
various types of tektite surfaces and natural,
chemically etched obsidian (Cosoites). The obsidian
material has been etched by the action of hot spring
waters that exhibit a pH of between 1.2 and 2.0,
depending on seasonal variations and amount of
rainfall in the area.
    The etching pattern found on the obsidian consists
of grooving and pitting. Single specimens may exhibit
two or more types of etching. The grooving is in a
random pattern and it does not follow flow lines or
cracks that are present in so e of the samples.
Generally, only one or two sides of the specimen have
been exposed to the action of the etching fluids or
gases. The remaining sides of the sample have been
protected by the parent mass or by a coating of
siliceous sinter and do not show any signs of etching.
 On many samples, where two or more sides are etched,
the types of etching on different sides are
dissimilar. Most of the recognized surface features
of tektites are found on these obsidian specimens.
     We conclude that most of the surface texture of
some tektites may be considered as secondary which may
have developed largely by chemical etching and by
[terrestrial] geological processes of weathering,
abrasion by wind sculpture [ventifacts], and transport
by water.





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Received on Tue 01 Oct 2002 03:13:59 AM PDT