a pool of Phyllite.

Compared to slate, phyllite is relatively coarser and indicates a slightly higher metamorphic grade, though these rocks still occur in the low-grade (e.g. lower greenschist-facies and below). Individual metamorphic grains are still too small (in most cases) to distinguish them with the unaided eye, but they are coarse enough to reflect light efficiently. In a schist, on the other hand, metamorphic grains are visible on hand samples. The foliation in phyllites is transitional between cleavage (fine-grained foliation) and schistosity (coarse-grained foliation): some authors refer to it as phyllitic cleavage.