[meteorite-list] Science page update / desert varnish on meteorites

From: STARSANDSCOPES at aol.com <STARSANDSCOPES_at_meteoritecentral.com>
Date: Mon, 1 Mar 2010 20:17:18 EST
Message-ID: <3998b.6b3eeda0.38bdc11e_at_aol.com>

Yes there is microscopic beauty even in desert varnish.

I love to examine the stuff in incident cross polarized light. Email me
for some eye popping 700X images. The minerals that make up the varnish
have different reflective properties which allow for almost irridized looking
effects when the polarization is played with.

I am just a layman but my observations (for what they are worth) is that
the varnish growth depends not only on the terrestrial environment but the
stone make up as well. Migrating minerals from within the meteorite feed
the surface.

I also have noticed small pieces of the meteorite broken off and grown
into the varnish as well as sand grains captured and encased in the varnish.
Occasionally I have seen meteorites that look jeweled or completely
encrusted in quartz sand grains.

Tom

In a message dated 3/1/2010 3:23:24 P.M. Mountain Standard Time,
oxytropidoceras at cox.net writes:
Greg wrote:

?I?m wondering if the formation of desert varnish
can vary depending on different biological and
environmental factors. Perhaps in one area a
similar thickness may take a shorter period of
time. 100,000 years is a long time, but I guess
not that long in geological time. This is interesting
in that some meteorites may have been sitting
on earth for a very long time.?

Below are some interesting pages about desert varnish:

Rock Varnish (desert varnish): An Internet Primer for
Rock Art Research by Ronald I. Dorn , Professor of
Geography Arizona State University

http://alliance.la.asu.edu/dorn/VarnishPages/VarnishPrimerIntro.html

Chapter 8 in Geochemical Sediments and Landscapes
http://alliance.la.asu.edu/dorn/VarnishPages/GeochemicalSediments/Geochemica
lSediments.html
http://alliance.la.asu.edu/dorn/DornCh08.pdf

Note: the above URL to Chap. 8, has numerous links to
PDF file of papers about rock varnish.

Desert Varnish
http://alliance.la.asu.edu/dorn/DesertVarnishDornFormat.pdf

Varnish Microlamination (VML) Dating

http://www.vmldating.com/

PDF files of various publication about rock varnish can
be downloaded from ?Selected Publications on
Methodology and Application of VML Dating? at:

http://www.vmldating.com/selectedpapers.html

Yours,

Paul H.
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Received on Mon 01 Mar 2010 08:17:18 PM PST