The Metallurgy of Pre-industrial Metals and Alloys

Unalloyed copper has a face-centred cubic (fcc) structure and a hardness of 40 HV in the annealed state. Native copper, which is not as pure as modern refined copper and which usually shows irregular grain sizes, has been found to be slightly harder with hardness from 45 to around 80 HV, and its hardness can be increased by cold-work to around 140 HV (135 HB), without any additional alloying elements, although it has only a very limited strength, even after significant reduction (see Bohme [11]; Coghlan [23]; Marechal [89]; Tylecote [173]).