English: Metamorphic rocks result from intense alteration of any previously existing rocks by heat and/or pressure and/or chemical change. This can happen as a result of regional metamorphism (large-scale tectonic events, such as continental collision or subduction), burial metamorphism (super-deep burial), contact metamorphism (by the heat & chemicals from nearby magma or lava), hydrothermal metamorphism (by superheated groundwater), shear metamorphism (in or near a fault zone), or shock metamorphism (by an impact event). Other categories include thermal metamorphism, kinetic metamorphism, and nuclear metamorphism. Many metamorphic rocks have a foliated texture, but some are crystalline or glassy.

Schist is an intermediate- to high-grade, foliated metamorphic rock. It is highly variable in appearance, depending on the mineral content, which is a function of the precursor rock and specific temperature-pressure conditions. Garden-variety schists form by metamorphism of phyllites. Schists typically have medium- to large-sized crystals, unlike the microcrystalline nature of slate & phyllite.

Schist's foliated texture (= crystals aligned into bands or stripes or layers) is often only seen when specimens are viewed on edge.

Talc schist is a metamorphic rock dominated by the mineral talc. Its color usually ranges from mottled, creamy white to mottled gray to light green. It has a pearly luster and a slick, soapy feel. Talc schist, like soapstone and steatite and the mineral talc itself, is very soft (H = 1). Unlike soapstone and steatite (= talcose, crystalline-textured metamorphic rocks), talc schist has a foliated texture (in this sample, the foliation is only seen when viewing the rock on edge). Some talc schists have formed by hydrothermal metamorphism of dolomitic marbles. Other talc schists are produced by hydrothermal metamorphism of serpentinized peridotites.