Mica
A mineral of a somewhat metallic lustre, that will permit of being split in thin plates, which can be substituted for glass in ship's lanterns, etc.; also for mounting transparencies in stoves. It is a widely diffused and plentiful mineral, entering largely into the composition of granite, mica-slate, etc. It consists essentially of silicate of alumina, with which are combined small portions of silicates of potash, soda, oxide of iron, oxide of manganese, etc. See GRANITE.