Final answer:
Phyllite is a type of foliated metamorphic rock that is distinguished from slate by its shiny, satin-like luster and more noticeable, yet fine-grained crystals. It indicates greater metamorphic change than slate, featuring visible grains and very thin layers of mica, describing a progression in the texture and composition of the rock.
Step-by-step explanation:
The subject of the question pertains to a type of metamorphic rock characterized by phyllitic foliation. Phyllite is distinguishable from slate by its shinier, satin-like luster and the presence of more noticeable, albeit still fine-grained crystals.
Unlike slate, which has smooth, flat surfaces due to slatey cleavage and very fine grains, phyllite has very, very thin, irregular layers of mica, usually showing a pale gray-green color and a satin sheen that covers the rock as a whole rather than individual flakes.
The uneven surfaces of phyllite and visible grains mark a progression from the dense, brittle characteristics of slate, as the rock undergoes increasing temperature and pressure during metamorphism.
Characteristics of Foliated Metamorphic Rocks
Foliated metamorphic rocks have a banded appearance due to the alignment of mineral crystals, where rocks such as slate, phyllite, and schist show a foliation texture without distinct color banding, differing from the layered gneissic foliation found in rocks such as gneiss.
Compared to non-foliated metamorphic rocks, which appear massive and structureless, foliated rocks like phyllite demonstrate a definite directional grain alignment and can split along parallel planes.