For the next two thousand years, humans mined and used copper. Where pure copper was found, it was chipped into small pieces from a big mass. The smaller pieces of copper were then hammered and ground into shapes, in the same way that stone had been treated before. But the copper pieces turned out to be too brittle for use. Luckily, humans learned to anneal copper. Annealing means to heat to a high temperature and then cool slowly. Annealed copper could be shaped and stamped and things made from it were less brittle.
Copper was sometimes found along with tin. When these two metals are mixed, the alloy, bronze, is much harder than both copper and tin. Bronze can be used to make stronger weapons and tools. Bronze knives could be made longer and developed into short swords or daggers. Other new weapons such as the mace and the lance also became possible.
When the supplies of native metals ran out, humans had to extract metals from their ores (compounds) dug out of the ground. They had to learn two important skills, mining and smelting. By 4000 BC, people were cutting shafts into the hillside in the Balkans to excavate copper ore. These people feared and respected the spirits, they believed, in the dark interiors of the earth. So they filled fine pots with produce from the outer world, and placed them in the mines. In this way they tried to compensate the spirits for the metals they took. These were the early days of mining.
Until tin was discovered, ancient bronze was made of copper and arsenic.
Ores had to be smelted to extract pure metal. Many of the ores were actually oxides. When they were heated with charcoal or coal, the carbon joined with the oxygen, and “reduced” the ore to metal.
Another major discovery of this period was that of casting. In casting, molten metals are poured into a mold, and then allowed to solidify. The solid metal can then be extracted from the mold. While casting, a single mold can be used over and over again to produce identical copies of the same object. Molded parts can be combined into more complicated objects.
The Bronze Age spanned from 3800 BC to 3000 BC. It was felt strongly in Britain and China and eventually spread to southern Europe. To bring together copper and tin to the same place, the Bronze Age saw a lot of trade in these metals. However, the Bronze Age had little effect on the mainland of Africa or the Columbian parts of South America.
Most of the inventions of the Stone Age were improved upon in the Bronze Age. Weapons, such as swords, axes, hammers, scythes, bows, cross bows, catapult and trebuchets were also developed in the Bronze Age. New forms of art such as pottery and sculpture emerged. Bronze lamps, tea kettles, vases and vials are often found in ruins from that period. Bronze figurines of gladiators and Olympians have also been found.
Aitcheson, Leslie. A History of Metals. Volumes 1 & 2. 1960. Interscience, New York, USA.
Cramb, Alan W. A Short History of Metals. Published online, <http://neon.mems.cmu.edu/cramb/Processing/history.html> accessed on 11-March-2009.
Habashi, Fathi. Principles of Extractive Metallurgy. Volume 1, Chapter 1. 1969. Gordon and Breach, Science Publishers, Inc., New York, USA.
Hartmen, Paul V. Stone Age, Bronze Age and Iron Age. An online history essay, <http://www.naciente.com/essay88.htm> accessed on 11-March-2009.