Not all dirt is brown. Soil takes on the colors of the surrounding minerals and debris. The soil in some area's is black and in places like Prince Edward Island it is bright red. Dirt consists of...
First, wash any dirt off of the exterior of the rock with soapy water and a brush. If a brown color remains, this color is due to staining, rock rind oxidation, or mineral content of the specimen....
Dirt is just the composition of ground up minerals, and plants over time, green dirt is indeed possible, but not probable for that kind green means the dirt attains some form of energy, and thus is...