Usually, the Tennessee River flowing through downtown Knoxville has a dark ... the brown color is mostly from an increase in the water's turbidity — marked by an increase in mud and dirt ...

"Iron in its purest form is a deep, dark ... iron in the dirt is exposed to air and water, it oxidizes, turning the rusty red you see in reclaimed mine dumps of the Mesabi," Aaron Brown writes.

Perhaps unsurprisingly, flea dirt looks a lot like, well…dirt. The dark pellets are often described as looking like coffee grounds in your pet’s fur or little black dots on your pet’s skin. Typically, ...