Why are the Red Rocks Red?

The answer is: iron! Sandstone is porous, and when water carrying dissolved iron drains through the sandstone, some of the iron is left behind, and it is this iron in the form of iron oxide, which is red, that coats the grains of quartz and gives it color.

The red rocks of Sedona, then, originated, some of them, from sediment in a sea or floodplain, while others originated from blown sand on dry land or in coastal areas. They can be distinguished by their colors, some more bright orange than others, some red, some tan. The bright orange rocks are more than 250 million years old. The white or grey rocks are either limestone that formed at the bottom of a sea, or else they are sandstone that has lost its red color because the color has been flushed out by water. There is also much basalt, extruded by volcanoes, in the area.