juamei wrote: Interesting stuff.
http://waynesword.palomar.edu/desertvarnish.pdf
Especially the fact that to make the petroglyphs they seemingly just chipped off the varnish.
I guess if someone can show the varnish is created at a consistent rate it would be usable as a dating tool.
Yes, the petroglyphs created by pecking or scraping the patina/varnish are rather dramatic. Instant polychrome works!
Thanks a million for that PDF, especially because I never read about the varnish being created by bacteria. That's pretty wild. "Extremophiles," eh? I think that's what we need to call ourselves when we're wandering around looking for old stones in the howling wind and rain.
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