Schist is a medium grade crystalline metamorphic rock. It's metamorphism from mudstone, shale, or sometimes igneous rock, is the result of higher pressure and temperature, than that needed to form slate. The crystals are larger than those of slates, and are visible to the unaided eye. Several minerals can determine the type of schist, i.e. garnet schist, talc schist, graphite schist, chlorite schist, but the most common type of schist is mica schist. Mica schist contains quartz with biotite mica or muscovite mica as the dominant minerals. This specimen from Ontario in Canada displays the silvery appearance that is attributed to muscovite mica.