Schist is a foliated metamorphic rock, formed from mudstone or some igneous rocks after they undergo high heat and pressure; similarly to Slate, but with a higher degree of metamorphism. It is characterized by large crystals that reflect light, making Schist a shiny stone, formed by these platy, elongated materials distributed in a specific orientation and often interleaved with quartz and feldspar.
It is considered a Schist any material with platy metamorphic minerals aligned in a certain way to characterize the stone with a distinct foliation, independently from its chemical and geological composition. Because of this texture, this rock can be easily broken along the direction of these platy mineral grains, characteristic known as schistosity. As said, this stone is formed from mudstone, which goes under high heat and pressure, and, depending on the levels of these two conditions, meta-morphs into different rocks, starting from Slate when the degree of metamorphism is low. If Slate then undergoes further metamorphism conditions, the mica grains will start to grow and this rock becomes another one called Phyllite. Once the process proceeds further, and the mica grains become big enough to be seen with the naked eye, the rock can finally be defined Schist. This last one can then become a Gneiss if further metamorphism occurs.
This stone doesn’t have many industrial uses, due to its low physical strength caused by these platy minerals, therefore it’s used only in areas on where the strength of the material is not crucial. Schist is also very often host of a variety of Gemstones. In the Mohs hardness scale, it scores between 3.5 and 4. Most of the Schists are commercialized as Granite, even though they are known to have a lower strength and therefore not being ideal for kitchen counter tops and other hard worn areas. Few of the most common ones are: Fusion Black, Kosmus and Matrix
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