Brass than in brass produced by cementation. These may be "natural alloys" manufactured by smelting zinc rich copper ores in redox conditions. Many have similar tin contents to contemporary bronze artefacts and it is possible that some copper-zinc alloys were accidental and perhaps not even distinguished from copper. However the large number of copper-zinc alloys now known suggests that at least some were deliberately manufactured and many have zinc contents of more than 12% wt which would have resulted in a distinctive golden color. By the 8th–7th century BC Assyrian cuneiform tablets mention the exploitation of the "copper of the mountains"
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