The earliest definite date usually assigned to true bronze casting is about 2500 B.C., i.e. 700 years or more after copper is known to have been in use; nevertheless numerous analyses show that copper artifacts of around 3000 B.C. sometimes contain small and variable percentages of tin. These may be regarded as "accidental bronzes."
One of the first things that the early coppersmith must have learned was that when he hammered copper he hardened it and, conversely, by heating the object he could soften or anneal it again. Thus the unalloyed metal could be fabricated and cut in a number of different ways. But when some unknown inventor conceived the idea of deliberately adding fixed proportions of tin ore to the melt, he produced true bronze and thereby started the Bronze Age. As bronze was harder, almost equally durable and decidedly easier to cast than copper, although much more liable to fracture if not properly made, its use spread rapidly. In the Mediterranean countries bronze was not supplanted for over 2,000 years and it lasted a good many centuries longer in north-western Europe, where methods of extracting and working iron were slower to follow those of Hallstadt and Rome. Meanwhile, both bronze and copper ran side by side. Museum labels on exhibits are not to be trusted unless analyses have been made and it is only in recent years that this has been systematically undertaken.The ancient tin was nearly always stream tin, nuggets of the ore being found in the stream gravels, perhaps in the search for gold. Tin ore occurs in Armenia, but everywhere in the world it is much rarer than copper. The main European deposits are in Saxony and Cornwall. British tin was widely famed, perhaps as far back as 1000 B.C. Knowledge of it probably reached the Continent indirectly; for as is well known there was a roundabout immigration from Spain through Ireland several hundred years at least before one can pick up the threads in England. No doubt Gaul and Kent must also have been in touch, but between Kent and Cornwall lay a vast, unbroken forest. The mining of British tin became quite an organized industry at a very early date. The metal was cast locally into ingots, and one of the probable smelters was on St. Michael's Mount, where abundant furnace scoriae from the slag have been found, and where also was situated the port of Ictis, whence traders passed into Gaul and so down to the Mediterranean. (1)