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 were initially influenced by the Earache roster (namely Godflesh, Napalm Death and Bolt Thrower). The German band Oomph! after their second album Sperm started to play industrial metal combined with elements of death metal and groove metal until the album Plastik. Sepultura singer Max Cavalera's Nailbomb, a collaboration with Alex Newport, also practiced a combination of extreme metal and industrial production techniques. A lesser-known example of industrial death metal is Meathook Seed, made up of members of Napalm Death and the Florida death metal group Obituary. An industrial music fan, Obituary guitarist Trevor Peres suggested drum machines for "The End