Speculum metal metal mixtures usually contain two parts copper to one part tin along with a small amount of arsenic, although there are other mixtures containing silver, lead, or zinc. The knowledge of making very hard white high luster metal out of bronze-type high-tin alloys may date back more than 2000 years in China although it could also be an invention of western civilizations. Such metals were used in sculpture and to make more effective mirrors than the more common yellow easily tarnishing bronze mirrors. In that era mirrors of speculum metal, or any precious metal, were rare and only owned by
Industrial metal later chose to experiment with industrial music. Industrial metal blossomed in the early 1990s, particularly in North America, where it would eventually sell close to 35 million units. It first became a commercial force in 1992 when Nine Inch Nails' "Broken" and Ministry's "" went platinum in America, though the latter took three years to reach that status. Both groups were nominated for the Best Metal Performance in the 1992 Grammy Awards, with Nine Inch Nails winning. Two years later, Nine Inch Nails released "The Downward Spiral", which debuted at No. 2, and would eventually go quadruple-platinum. This record is