* Slate: Formed under relatively low-grade metamorphic conditions, slate is characterized by its fine-grained texture and ability to split into thin, flat sheets.
* Phyllite: As metamorphic grade increases, slate transforms into phyllite, which has a slightly coarser texture and a slightly more lustrous sheen.
* Schist: With even higher metamorphic grade, phyllite turns into schist, which is characterized by a more pronounced foliation (layered structure) and the presence of larger mineral crystals.
* Gneiss: Under extremely high-grade metamorphic conditions, schist can transform into gneiss, a metamorphic rock with a more distinct banding of light and dark minerals.
The exact metamorphic rock formed from shale also depends on the original mineral composition of the shale. For example, a shale rich in calcium carbonate might form a marble under high metamorphic grade.
