Rock wool insulation provides thermal and sound insulation in the automotive and building industries. It is much like fiberglass insulation, but manufacturers make it from strands of molten rock and minerals instead of glass. As of 2015, rock wool is about 20 percent more expensive than fiberglass insulation.
Rock wool is slightly denser than fiberglass insulation. It has a higher R-value and is better at providing sound insulation. The higher density increases the fire resistance of rock wool in comparison to fiberglass. While fiberglass insulation melts at approximately 1,100 degrees Fahrenheit, rock wool is able to withstand temperatures up to 1,800 degrees Fahrenheit.