A Classification of Metamorphic Rocks

Metamorphic rocks can be classified according to the location of occurrence, chemical composition, texture and structure, and mineralogical composition.
The classification with regard to location was done in the past but is not used today. The chemical classification is primarily used for carbonate metamorphic rocks because they are easy to dissolve. This classification is not common in Silica based rocks.
Silicate rocks are classified with regard to the texture and structure of the rocks as follows
1.  Foliated Rocks
According to the degree and size of foliation, it is further subdivided into the following categories
-Slaty foliation
-Phyllitic Foliation
-Shistose foliation
-Gneissic Foliation
2.  Non Foliated Rocks
non foliated rocks are further subdivided into granular rocks where individual grains can be identified, and massive rocks in which no such features can be found.
After visual observation of the rocks and the determination of the relative abundances of minerals, the rocks are given names that indicate the principal minerals and the structural and textural features. For example, "Garnet, Sillimanite, Graphite Schist" is a rock that contains amounts of the minerals mentioned in that order and has a Shistose Foliation.