Mica is a group name for a number of hydrous aluminosilicate minerals, such as muscovite, phlogopite, biotite and lepidolite. Muscovite and phlogopite are the principal commercial micas. Muscovite of commercial interest occurs in sheet and flake form associated with quartz and feldspar in pegmatites. Phlogopite occurs in sheet and flake forms in basic ferromagnesian rocks. Deposits of particular interest occur in eastern Ontario and southeastern Quebec, although occurrences have been noted in several other provinces. There is only one producer of mica in Canada, Suzorite Mica Products Inc., a division of Lacana Petroleum Limited, which operates a deposit of phlogopite mica in Suzor Township, Quebec. The bulk of production is exported to the United States, Japan and Europe. There is no current production of muscovite in Canada; our limited requirements are met by imports from the United States, France and India. Mica has several unique properties, that is, uniform basal cleavage, high dielectric strength, toughness and flexibility, which have resulted in its broad use in electric and electronic applications. Other uses include filler and strengthener in paint and plastics, and as a substitute for asbestos in joint-filling compounds. Mica may be processed and used in the dry-ground, water-ground and micronized form. Unique techniques are being developed for treating mica flakes, such as acid leaching and surface coating, to extend the use of mica, particularly in plastic composites. Vermiculite closely resembles mica but differs in one important aspect: it expands on heating to make a lightweight product that is useful as an insulator in building construction and as a lightweight aggregate in concrete. There is no production of vermiculite ore in Canada; however, imported crude vermiculite is expanded at several Canadian plants for insulation and concrete applications. Mica and vermiculite processing and beneficiation have been studied extensively by CANMET during the past 50 years. Beneficiation studies of these minerals by CANMET and other organizations are summarized in the appendices.