This group of alumino-silicate minerals is widely used in making electrical insulators

Answer: Option D

Sheet mica is used principally in the electronic and electrical industries. Its usefulness in these applications is derived from its unique electrical and thermal insulating properties and its mechanical properties, which allow it to be cut, punched, stamped, and machined to close tolerances. Specifically, Mica is unusual in that it is a good electrical insulator at the same time as being a good thermal conductor.