desert varnish
n.
thin and shiny layer that is reddish brown or black in color composed of iron and manganese oxides which coats the surfaces of many desert rocks that are exposed
Desert varnish
Desert varnish, or rock varnish is a dark coating found on exposed
rock surfaces in
arid environments. It is one of fourteen different types of rock coatings.
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desert varnish
A thin, shiny red-brown or black layer, principally composed of iron manganese oxides, that coats the surfaces of many exposed desert rocks.