crystalline schist
thumb|A schist showing characteristic scaly schistose texture caused by platy mica|micas Schist ( ) is a medium-grained metamorphic rock generally derived from fine-grained sedimentary rock, like shale. It shows pronounced schistosity (named for the rock). This means that the rock is composed of mineral grains easily seen with a low-power hand lens, oriented in such a way that the rock is easily split into thin flakes or plates. This texture reflects a high content of platy minerals, such as mica, talc, chlorite, or graphite. These are often interleaved with more granular minerals, such as fel
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Crystalline schist is a medium-grained metamorphic rock formed from fine-grained sedimentary rocks like shale, characterized by flat, platy minerals (such as mica) that are oriented in a way that makes the rock split easily into thin flakes or plates. This distinctive texture and composition make schist useful for understanding how rocks are transformed under heat and pressure deep within the Earth, and historically it has been valued for roofing and other construction purposes.
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7 sectionsContents
- Etymology
- Definition
- Formation
- Engineering considerations
- See also
- References
- External links
thumb|A schist showing characteristic scaly schistose texture caused by platy mica|micas Schist ( ) is a medium-grained metamorphic rock generally derived from fine-grained sedimentary rock, like shale. It shows pronounced schistosity (named for the rock). This means that the rock is composed of mineral grains easily seen with a low-power hand lens, oriented in such a way that the rock is easily split into thin flakes or plates. This texture reflects a high content of platy minerals, such as mica, talc, chlorite, or graphite. These are often interleaved with more granular minerals, such as feldspar or quartz.
Schist typically forms during regional metamorphism accompanying the process of mountain building (orogeny) and usually reflects a medium grade of metamorphism. Schist can form from many different kinds of rocks, including sedimentary rocks such as mudstones and igneous rocks such as tuffs. Schist metamorphosed from mudstone is particularly common and is often very rich in mica (a mica schist). Where the type of the original rock (the protolith) is discernible, the schist is usually given a name reflecting its protolith, such as schistose metasandstone. Otherwise, the names of the constituent minerals will be included in the rock name, such as quartz-felspar-biotite schist.