A Metal for All Ages
Voynick, Steve, The World and I
Copper has taken us from the Stone Age to the Information Age.
In the long Stone Age of human prehistory spanning hundreds of thousands of years, our ancestors became masters at exploiting the available materials from plants, animals, soils, and stones to meet their needs for clothing, shelter, weapons, tools, and decorations. Their knowledge and use of metals, however, was limited to tiny bits of native copper and gold collected from rocky outcrops and gravels.
No tools or weapons could be made of a metal until the monumental turning point some 7,000 years ago when an early metallurgist somewhere in Asia heated the blue-green rocks associated with the bits of metallic copper in a bed of drafted, glowing coals. From the vantage point of today's scientific knowledge, we can say that the combination of intense heat and direct contact with carbon and free oxygen drove off the oxygen and carbon within the copper minerals, leaving behind a small pool of molten, metallic copper.
Today, metallurgists call this reaction--intensely heating a metal-bearing mineral in the presence of free oxygen and carbon--simple reduction smelting. Few discoveries have had greater significance. The realization that copper could be derived from certain rocks that had no metallic appearance represented a quantum leap in man's understanding of the natural world. By greatly increasing the supply of copper, smelting lifted mankind from the Stone Age into the Copper Age.
A metal of utility
The greatest steps on the ladder of technological advancement are named for the materials or forces that made them possible--the Stone Age, Copper Age, Bronze Age, Iron Age, the Age of Electricity, and the Information Age. As various cultures came into the Copper Age, the availability and use of metals greatly stimulated their technological development. Metals have now taken us into the Age of Electricity and on into the Information Age. In the seven millennia since humankind laid aside its stone tools, only one utilitarian metal has been with us every step of the way--copper.
Gold and copper both occur in nature in the metallic, or flee, state, and by 10,000 B.C. certain European and Asian cultures were collecting small bits of them.
Because of its gleaming, sunlike color and a softness that allowed it to be easily hammered into ornaments, no doubt gold was the more appealing metal. Copper had a rich, reddish hue and was considerably harder than gold. Although copper was more difficult to hammer, its fabricated shapes proved hard enough to have utilitarian value as simple tools and implements. The rarity of metallic copper, however, precluded the possibility of significant advances in metalworking technologies.
Metallic copper usually occurs in rock outcrops where the atmosphere and water have oxidized copper sulfides into copper oxides and two copper carbonates, brilliantly colored blue azurite and green malachite. These copper minerals are much more abundant than metallic copper. Yet, despite this close association in outcrops, Stone Age man apparently made no connection between the metal and the minerals. By 5000 B.C., some Asian cultures had learned to melt copper in drafted charcoal fires. From that point, the discovery of crude smelting technology was only a matter of time.
Chronologically, the Copper Age--the period when a culture's tools and weapons were made of copper--is of strictly local value, since the metal came into use at radically different times in various parts of the world. The same is true for the Bronze Age.
Bronze is an alloy made primarily of copper and small amounts of tin, a metal that also occurs free in nature. Archaeologists now believe that bronze originated in Thailand about 4500 B.C., and was probably first produced through the accidental mixing of copper and tin ores. But accidental or not, bronze was harder than copper, early metalworkers realized, and it had superior casting qualities -- ideal attributes for fashioning improved tools and weapons. …