The basis for identification and classification of non-foliated metamorphic rocks is what?

Answer 1

For that, for clay based stones, you use mineralogy and the different facies. As things get progressively more metamorphosed, they are characterized by different types and combinations of minerals, and these are identified as greenschist/blueschist/amphibolite facies, and so on.

Other metamorphic rocks which did not originate from pelitic stones originally are classified in kind of a mish-mash way, absed on your starting point and again how altered they are. A lot of it is done on the texture and degree of melting a rock has undergone, and again the base texture. these would include such rocks as hornfels and quartzite.