Explanation
Low grade metamorphic rock with phyllitic structure. The original rocks are usually argillaceous rock (or argillaceous rocks containing siliceous, calcareous and carbonaceous rocks), siltstone, intermediate and acidic tuff, etc., which are formed in the bottom greenschist facies stage of regional low-temperature dynamic metamorphism or regional dynamic heat flow metamorphism. The hairdressing surface of the microcrystalline chip has a silky luster. The metamorphic degree is between slate and schist.
Classification
Natural materials and products -> Mineral materials