Thank you for posting this. I’ve always wondered about the varnish and how it is formed.
Anyone who has spent time in a desert has probably noticed many dark streaks or patches on the rocks. I expect that most people simply look at these dark streaks and think they are simply stains like a stain on a cement driveway or that line of rust color running down a wall from a rusty nail above. No big deal right? But what if you were shown a picture of the same rock taken 50 years earlier and the stains looked identical to you? You might start to wonder just how old those stains are on those rocks. A week ago I posted pictures (NH Photography: Desert Varnish around Moab UT) of rocks with shiny black or orange varnish on them from my trip to Utah this summer. I want to explore the origins of this varnish a further today.
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