Discovering Metals— A Historical Overview

THE ANCIENT WORLD passed from the Stone Age through the Bronze and Iron Ages to our modern developed society—a society that is dependent on metals and alloys for its very existence. However, an impressive body of metallurgical knowledge developed in the thousands of years since ancient man first found copper and became curious enough to investigate the behavior of this naturally occurring, relatively pure, native metal. Metallurgical knowledge evolved from an art to a science, until the body of scientific knowledge on how each metal and alloy behaves has become quite extensive. A historical summary of developments in metallurgy from the use of native metals to the electrolytic refining of aluminum in 1884 is provided in Table 4.1. Six metals were used by prehistoric man: gold, silver, copper, tin, lead, and iron. Gold and silver were too soft to be useful for much except decoration. Copper could be hardened by hammering or forging and was therefore useful as a tool but had little value as a weapon. Bronze, developed by alloying copper with tin, had useful strengths, could be hardened by forging, and could be cast to shape. The discovery of bronze significantly altered the development of civilization. Lead was soft, easily worked, and could be made into vessels; later in history it was made into pipes such as those used to transport water in the early Roman Empire. Iron was so important to civilization that its discovery led to the Iron Age and a transition from the Bronze Age.