Sheet mica splittings are available from Van Dyke’s Restorers, 800-558-1234, http://www.vandykes.com. My catalog is getting a little old and out-of-date but it is available in an 18″ x 36″ x.015″ size and an 18″ x 18″ x .015 size. It is a bit pricy.
It’s used as a shade material in arts and crafts style lamps, among other things.