Metamorphic Facies

Metamorphic facies is a more sophisticated extension of the grade concept to include pressure (geobarometry as well as temperature (geothermometry to the interpretation of metamorphic rocks.

The indicator minerals become groups of minerals or mineral assemblages that characterize a particular region of P/T space.

Again the names and numbers are not important but the concept of using mineral assemblages to characterize the P/T conditions of recrystallization is key.