A measure of the relative intensity of metamorphism. In pelitic rocks (see pelite), an increase of metamorphic grade is marked by a progressive dehydration of the mineral assemblages present whilst in limestones and impure limestones an increase in grade is marked by progressive decarbonation of the mineral assemblages present. In general, mineral assemblages stable at progressively higher pressures and temperatures characterize an increase in metamorphic grade (e.g. garnet grade).
Subjects: Earth Sciences and Geography.