Nonfoliated: lack flat crystals with parallel alignment. Crystals are about the same size in an interlocking crystalline texture.  Quartz, feldspar, and calcite commonly produce nonfoliated textures.

Foliated: contain minerals that are aligned in parallel planes.  Common minerals are:

Biotite
Muscovite
Chlorite
Amphibole (hornblende)

Foliated rocks often appear to be layered. Directed pressure was perpendicular to the planes of foliation.

There are 4 distinct types of foliation:

SLATY: alignment of microscopic platy minerals – gives a slaty cleavage.

PHYLLITIC: foliation of platy minerals that can just be seen with a hand lens.  Appears shiny and does not cleave as well because foliation planes may be deformed.

SCHISTOSE: foliation defined by minerals that can be seen with the naked eye. Platy minerals predominate but quartz and/or feldspar may also be seen.

GNEISSIC: a coarse foliation defined by minerals segregating into roughly parallel bands, which are light (quartz and feldspar) and dark (micas + pyroxenes) colored.

During very high-grade metamorphism, the quartz and feldspar melt to form a Migmatite – mixed igneous-metamorphic rock.

Beware of Relict Textures: this occurs whenever textures in the original rock survive the metamorphic event, especially in low-grade metamorphic rocks. For example, cross bedding in sandstone, sedimentary bedding, metamorphosed limestones can display layering because of layered impurities during deposition.