A closer look
Those mysterious, shiny black and red streaks coating sun-baked desert cliffs are not geological stains; they are the ultra-slow-motion artwork of microscopic life. For thousands of years, specialized metallogenium bacteria extract trace amounts of manganese and iron from airborne dust, oxidizing them to build a protective chemical sunscreen known as desert varnish. This biological crust grows as slowly as the thickness of a piece of paper every thousand years, creating the perfect, dark metallic canvas that ancient civilizations like the Anasazi scraped away to create their famous rock art.
