Although metamorphic rocks comprise a large part of the crystalline crust, relatively few data concerning metamorphic rock densities are available. In this paper, we present rock densities from seven different metamorphic terrains. Mean densities for rock types range from 2.65 gm/cm 3 for biotite granite gneiss to 3.04 gm/cm 3 for diopside granofels. Mean rock densities for metamorphic terrains range from 2.70 to 2.86 gm/cm 3 . Rock density may decrease in the lower part of the upper crust. Most mean rock densities for metamorphic terrains fall between 2.70 and 2.79 gm/cm 3 ; the mean density of 2.67 gm/cm 3 commonly used for the upper crystalline crust is too low.