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 with the success of groups such as Nine Inch Nails. The industrial metal movement began to fade in the latter half of the 1990s. Though electric guitars had been used by industrial artists since the early days of the genre, archetypal industrial groups such as Throbbing Gristle displayed a strong anti-rock stance. British post-punk band Killing Joke pioneered the crossing over between styles, and was an influence on major acts associated with industrial metal such as Ministry, Godflesh, and Nine Inch Nails. Another pioneer industrial rock group, Big Black, also impacted some later groups. By the late 1980s industrial and