On average, mineral wool is made of 75 percent post-industrial recycled content. It comes in both blanket and loose-fill forms. Additional chemicals to make it fire-resistant aren't required, much like cotton insulation. Most often, mineral wool is a classification for two kinds of insulation: Rock wool is a man-made material that includes natural minerals, and slag wool is a man-made material that comes from scum called blast furnace slag that collects on molten metal.
There are hundreds of mineral wool companies in the United States; however, the U.S. Department of Energy notes that there is a Canadian company that produces a superior product.