Schist
The schists are a group of metamorphic rocks which have lamellar (plate-like) minerals, such as micas, chlorite, talc, hornblende, graphite, and others. Quartz often occurs in drawn-out grains so that a form called quartz schist is produced. By definition, schist contains more than 50% platy and elongated minerals, often finely interleaved with quartz and feldspar. Schist often contains garnets.