desert varnish

American  

noun

1. the dark, lustrous coating or crust, usually of manganese and iron oxides, that forms on rocks, pebbles, etc., when exposed to weathering in the desert.

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Etymology

Origin of desert varnish

First recorded in 1900–05

Example Sentences

As we wound through the last stretch of canyon, which she called Nature’s Hallway, Begay showed us colorful formations on the rock called Navajo, or desert, varnish — the product of thousands of years of rain causing minerals such as iron to streak down the walls.

From Washington Post

A relaxing cruise through Lake Powell features views of the Glen Canyon Dam, the second-highest concrete arch dam in the United States, as well as the impressive Navajo Canyon, whose 600-foot-high rock walls are covered in desert varnish.

From Washington Post

Many of the images were carved into desert varnish, a thin red to black coating found on exposed rock surfaces.

From Los Angeles Times

Even these days, she’s known to take off on a whim to explore Red Rocks or Canyonlands National Park, hiking along streams and exploring the ruins built into canyon walls where the desert varnish has darkened the pictographs.

From Seattle Times

As we bounced along in an open Jeep, the canyon deepened in colonnaded spires and 800-foot-high cliffs streaked with black “desert varnish” — discoloration from centuries of rain and sun.

From New York Times