Noun
desert varnish (countable and uncountable, plural desert varnishes)
(geology) A dark coating found on exposed rock surfaces in arid environments.
Desert varnish is usually around one micrometer thick and represents nanometer -scale layering. Source: Internet
Desert varnish often obscures the identity of the underlying rock, and different rocks have varying abilities to accept and retain varnish. Source: Internet
Geology: An Introduction to Physical Geology 4th ed. Pearson Education p. 585 It has been suggested that desert varnish should be investigated as a potential candidate for a " shadow biosphere ". Source: Internet
Desert varnish: the importance of clay minerals. Source: Internet
Even though it contains high concentrations of iron and manganese, there are no significant modern uses of desert varnish. Source: Internet