[meteorite-list] Science page update / desert varnish on meteorites
cdtucson at cox.net
cdtucson at cox.net
Mon Mar 1 23:22:07 EST 2010
Tom,
Very interesting. Thank you for your response here.
I look forward to reading about how this could be. I would have never guessed that the rock's own minerals could migrate into the surface varnish.
I guess as the saying goes. You learn something new every day. This is why I love this list.
I have always checked for Desert varnish by applying simple drug store hydrogen peroxide and watching it fizz. No fizz means no desert varnish.
But it never occurred to me that meteorites could be old enough to also have desert varnish. Guess I better recheck my old black desert varnish covered rocks again.
Please do send me pictures. Thanks again. Carl
--
Carl or Debbie Esparza
Meteoritemax
---- STARSANDSCOPES at aol.com wrote:
> 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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