Colors of Rocks

The Monument Valley rocks are composed of sand, silt, and mud grains with finer grained material between the grains. Most grains are not red; it is the fine-grained material, which includes iron oxides, between the grains that is red. It turns out that only a little bit of iron (even less than 1%) may be enough to make the entire rock look red.

Here are some generalizations about the color of rocks:

Generally, most really red rocks were deposited on land, not beneath the water or at high temperatures or great depths.

Back to the Geologist's Observation Page