Mineral Wool is the thread-like filaments produced by the action of steam or compressed air upon vitreous substances in a molten state. The product is also called silicate cotton by some, as its principal material is silica. The fibers produced are used to incase boilers and steam-pipes, thereby preventing the diffusion and waste of heat. It also is of great value in deadening sounds. As it will not burn or rust and is not subject to the depredations of insects, it is of great value in many mechanical adjustments. The use of it increases every year. The best mineral wool is obtained from the melting of a cinder made by mixing together four parts of orthocase feldspar and six parts of dolomitic limestone.