Block Mica is knife-dressed mica with a minimum thickness of 7 mils (0. 18 mm). Block Mica is available in sizes up to 12 to 14 (30 to 35 cm) square. Block Mica larger than this is rare and even it was available it would be far too costly for most applications. Block Mica is available in sheets with an average thickness between 7 mils & 30 mils (0. 1 8 mm & 075 mm) Block Mica is supplied in both natural (random) and calibrated thickness as required by the customer. After splitting into a specified thickness the mica is then cut and punched to the required size and shape to meet the requirements, typically, of an electrical application.