sedimentary

Desert Varnish on Sandstone

Quartz Arenite with Iron-Manganese Oxide Coating

AI-generated identification · may be incorrect

Hardness: 6.5-7 (sandstone matrix), Color: orange-brown to near black, Luster: dull to sub-metallic, Texture: porous under-layer with a thin, hard mineral skin

Hardness: 6

Identified July 17, 2026More sedimentary →

Explore Desert Varnish on Sandstone in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness: 6.5-7 (sandstone matrix), Color: orange-brown to near black, Luster: dull to sub-metallic, Texture: porous under-layer with a thin, hard mineral skin

Formation & geological history

Formed over thousands of years as manganese and iron oxides are deposited by bacteria or wind-borne dust and then cemented to rock surfaces in arid environments. Typically found on Paleozoic or Mesozoic sandstones.

Uses & applications

Geological study, archaeological dating (petroglyphs), and desert landscape aesthetics.

Geological facts

Desert varnish is often only micrometers thick, yet it can be thousands of years old. Ancient civilizations used it as a canvas by scratching through the dark varnish to reveal the light rock underneath, creating petroglyphs.

Field identification & locations

Identify by the dark, often shiny or leathery thin coating on exposed desert rock faces. It is common in the Southwestern United States, Northern Africa, and the Middle East.