Physically, these are Metamorphic-Argillaceous rocks, which has developed a well-marked splittable cleavages with or without developed recrystallization & spots/knots of minerals like garnet, pyrite, andulasite, etc. They are normally fine to medium grained, moderately hard & compact, less homogeneous with varying textures & shades. It has an ability to split into thin layers along the plane of cleavages due to flattened & elongated minerals along the plane of cleavage.

Chemically, they are Multi-Mineral, metamorphic argilaceous rocks made of an aggregate of minerals and colloidal substances. Essentially mineral composition includes quartz, mica, chlorite, sericite & oxides of iron with occasional spots/knots of minerals like garnet, pyrite, andulasite, etc.