Book 16, Question 18
Why Are Desert Rocks So Often Red, Orange, or Pink?
Many desert rocks contain iron! When iron meets air and a little moisture, it rusts, forming red and orange minerals. That rust coats the sand grains and paints the rocks.
More fun facts
- The red, pink, yellow, and brown colors of Utah's red rock country come mostly from one element, iron.
- When iron joins with oxygen it becomes iron oxide, a kind of rust.
- Hematite, a red iron mineral, is named from the Greek word for blood.
- In the Navajo Sandstone, white quartz grains are coated with a thin layer of red hematite.
- Where underground water washed the iron away, the sandstone turned pale pink or white.
- Round iron balls called Moqui marbles weather out of the Navajo Sandstone, some about 1 to 4 inches across.
Sources: geology.utah.gov, National Park Service
Questions kids ask
Why are some desert cliffs white on top?
Water moving through the rock long ago washed away the red iron coating, leaving pale sand grains.