Mica block is acquired in size as huge as 30 to 35 sq. cm. (12 to 14 square inches) beyond which we can say it is rare as well as too costly. It is procurable in sheets with an average thickness between 0.18m to 0.75m (0.007 to 0.030 inches). In these mica blocks the presence of magnesium can be detected with the preeminence of potassium and Phlogopite.
In short, we can say Knife dressed Sheet of Mica with a minimum thickness of 0.18 mm (0.007 Inch), is called Block Mica.