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

From: cdtucson at cox.net <cdtucson_at_meteoritecentral.com>
Date: Mon, 1 Mar 2010 23:22:07 -0500
Message-ID: <20100301232207.ATT70.933764.imail_at_fed1rmwml33>

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.
______________________________________________
Visit the Archives at  
http://www.meteoritecentral.com/mailing-list-archives.html
Meteorite-list  mailing  list
Meteorite-list at meteoritecentral.com
http://six.pairlist.net/mailman/listinfo/meteorite-list   
______________________________________________
Visit the Archives at http://www.meteoritecentral.com/mailing-list-archives.html
Meteorite-list mailing list
Meteorite-list at meteoritecentral.com
http://six.pairlist.net/mailman/listinfo/meteorite-list
Received on Mon 01 Mar 2010 11:22:07 PM PST


Help support this free mailing list:



StumbleUpon
del.icio.us
reddit
Yahoo MyWeb