White mica or muscovite is valuable, especially if in large pieces, which cleave easily into thin plates. It is used for chimneys for incandescent gas lights and Davy lamps, for smoke preventers or hoods for lamps and gas burners; also in place of glass in the fronts of gas stoves, etc.; and in some countries it is used in place of glass for windows. The rough stuff is ground up and used as a paint, and the fine scaly kinds are coloured and used in place of bronze colours. The black mica, or biotite, is of no value. Sometimes black talc is called black mica. In addition to the uses above mentioned, mica is put into room ventilators, and it is very largely employed in electrical machinery as a non-conductor.