Ametamorphic rock can be classified according to its

Texture and composition

Explanation:

The rocks that are formed due to the changes in rocks that come about due to intense heat and pressure are referred to as metamorphic rocks. The metamorphic rocks can be classified based on their texture as well as the composition of the minerals that constitute it. The textures on the rocks can be either foliated or non-foliated and the composition can consist of whereas minerals such as sillimanite, kyanite, staurolite, andalusite, etc.The texture can further be used to divide the rocks into slaty, schistose, gneissose, granoblastic and hornfelsic.

4, two dominant and two recessive