Brass pendant in form of human mask probably badge of Ogboni society, made by Yoruba, Southern Nigeria, West Africa, 1801-1920

Copper alloys have a unique combination of characteristics.They have high thermal and electrical conductivity, high corrosion resistance and high ductility and formability, as well as attractive colours. The best known copper alloys are the brasses which are composed of copper and zinc. Brasses containing less than 36% of zinc are ductile when cold and can be worked into complex shapes without the necessity of annealing. Brasses containing more than 36% of zinc are harder and stronger than those containing less, and although such brasses are less workable at room temperature their plasticity is increased at high temperatures. Consequently they are usually shaped by hot-rolling, extruding and casting.