Why is dirt almost always a brown color?

Question

Why is dirt almost always a brown color?

In: 329

Answer 1

Aluminum oxide. The most common metal in the Earth’s rust is Aluminum, the most common element in the Earth’s crust is oxygen. Put them together and you get Aluminum oxide. There’s also a lot of silicon, meaning silicon dioxide (glass) is also very common (silicon is the second most common element in the crust, aluminum being 3rd) but it doesn’t have much color of its own, so the aluminum takes over.

Places with red sands generally have more iron, getting a red color from iron oxide (ie Mars) and black sands are created from volcanic activity, creating basalt which is black due to minerals like augite.