Sometime around 3000 BC the probably accidental inclusion of a
tin-based mineral, cassiterite, in the copper ores provided the next
step in technology: the production of the alloy bronze, a mixture
of tin and copper. Tin gives bronze an additional hardness that pure
copper cannot match, allowing the production of superior tools
and weapons. This discovery of alloying and solid solution strengthening—the hardening of one metal by adding another—was of
such importance that it, too, became the name of a new era: the
Bronze Age.