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"
Ampco Metal Ampco Metal AMPCO METAL is a diversified speciality alloy engineering company working primarily in copper based alloys, non-sparking safety tools and speciality welding products. The Switzerland based company is a manufacturer of engineered alloys of different compositions and properties, intended for specific uses in the aerospace, automotive, energy conservation, manufacturing and other industries. It also produces non-sparking safety tools for the oil industry, as well as the firefighting and fire prevention sectors. Additionally, AMPCO METAL provides engineering, machining and welding advice to the industry, in matters involving its speciality copper, aluminium-bronze and other alloys. AMPCO METAL currently employs approximately 250