Schist is a medium-grade metamorphic rock with medium to large, flat, sheet-like grains in a preferred orientation nearby grains are roughly parallel. It is defined by having more than 50% platy and elongated minerals, often finely interleaved with quartz and feldspar. These lamellar flat, planar minerals include micas, chlorite, talc, hornblende, graphite, and others. Quartz often occurs in drawn-out grains to such an extent that a particular form called quartz schist is produced. Schist is often garnetiferous. Schist forms at a higher temperature and has larger grains than phyllite. Geological foliation metamorphic arrangement in layers with medium to large grained flakes in a preferred sheetlike orientation is called schistosity
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