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

[STARSANDSCOPES 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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