Mass per unit volume, expressed in grams per cubic centimeter. Rock or formation densities are usually measured as either saturated bulk densities or grain densities. For gravity interpretation, the contrasts between rock bulk densities are of primary interest since these contrasts are responsible for the anomalous gravity field.

Rock bulk densities have been shown to vary as a function of geologic age, lithology and depth of burial. Rock densities typically range from 1.9 g/cm³ to 3.0 g/cm³.