[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-listReceived on Mon 01 Mar 2010 11:22:07 PM PST |
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