ancient copper head from Iran
This copper head was made thousands of years ago. It is no longer
bright because, in time, copper is covered with a greenish coating
called patina.Courtesy Metropolitan Museum of Art, New York.
pure copper and copper ore
The Bronze Age minerals
Do you have a brand-new, shiny penny? If so, you know what the mineral
called copper looks like. Pennies are made of almost pure copper—a
gleaming, reddish-brown metal.
Copper was one of the first metals that people used. During the Stone
Age, people had only stones and bones with which to make weapons and
tools. But about ten thousand years ago, people found that they could
pound and shape lumps of copper into knives, spearheads, and bracelets.
Those people of long ago found great lumps of pure copper in the earth.
But people have taken copper out of the ground for thousands of years.
Now there is very little pure copper left. Today, most of the copper we
find is mixed with other minerals. Minerals that contain copper are
called copper ores.
Copper is an important metal. Most of the wires that carry electricity
into our houses and factories are made of copper. This is because
electricity moves better through copper than through any other common
metal.
Tin is another metal that people have used for a long time. It is a
bluish-white metal that is heavy and soft, like copper. It comes from a
brownish, glassy, mineral called cassiterite. People of long ago often
found pebbles of cassiterite in riverbeds. Today, most cassiterite has
to be dug out of the earth.
About five thousand years ago, ancient people learned how to mix tin
with copper. By melting tin and copper together, they could make a metal
called bronze. Bronze is much stronger and tougher than either tin or
copper. From bronze, the ancient people made swords, helmets, armor,
cups, bowls, and many other things. When people learned to make bronze,
it was the end of the Stone Age and the beginning of the Bronze Age.
When we think of tin, we usually think of tin cans. But tin cans are
really made of iron or steel covered with a thin coating of tin. The tin
gives the cans a shiny look and keeps the iron or steel from rusting.
