Explanation

It is also called slaty cleavage. It is a structure formed by low-grade regional metamorphism of argillaceous rock, and is the characteristic structure of slate. It is parallel or oblique to the original rock bedding, usually neat and smooth, sometimes with a small amount of sericite, chlorite, etc., showing weak silky luster. Thermal contact metamorphism can also form slate? But its plate like structure may be the plate like bedding of the original rock, rather than the plate like cleavage formed by stress.

Classification