1
Precious Metals
by Brandon Guymon
http://www.kidspast.com/
P
recious metals: Gold, silver, platinum, brass, iron, and
bronze; these metals are closely associated with our
history. Mankind has searched for and fought over these
metals since the end of the Neolithic (Stone Age). Metal has lifted
mankind’s technology from simple stone tools and weapons to
computers and space travel. Without our precious metals we
would still be living in tribes, wandering in search for food.
The Neolithic ended when people stopped using stone
tools and started to use tools made out of metal. No one really
knows how or why people started to use metal tools rather than
stone; the inventors of metal tools didn’t write anything down.
Scientists think people started using copper and gold for
ornaments and jewelry before they started using metal for tools.
The reason scientists think jewelry came first is because they have
found human skeletons surrounded by metal jewelry and stone
tools. Archeologists found the Varna Necropolis in 1972.
(Necropolis is a fancy scientist word for graveyard.) The gold and
copper artifacts found in Varna Necropolis are mostly beads and
other forms of jewelry. The tools found in the graves are mostly
made from stone. These graves have been dated to 4700 to 4200
BCE.
It didn’t take long for people to start making tools out of
copper. In fact, Otzi, the Iceman, was found high in the Alps with
several artifacts including a flint knife, flint-tipped arrows, and a
copper-bladed ax. His body and his tools were preserved in the
glacier ice that covered them. He is the oldest human mummy
around. His body dates back to approximately 5300 BCE; so, about
the same time as the Varna people.
2
So why use copper and gold? Copper and gold can be
found as native metal. Native metal means you can pick up a
nugget of copper or gold and pound on it with a hammer and
make stuff out of it. You don’t have to heat it up or melt it out of
the rock. However, if you pound on unheated native metal too
much it will crack. So about all you can do with native metal is
make beads or very simple tools. If you heat native copper, you
can make better tools.
Otzi’s ax is the product of a different process. Most copper
in the world is not the pure native copper. Most copper is found
in what is called an ore. An ore is a mixture of metal, rock and
other junk. At some point in time people learned (again, scientists
don’t know when or how) that if you heat up crushed ore to a
very high temperature the metal will melt and leave the junk you
don’t want behind. This process is called smelting. Otzi’s ax blade
was made from copper smelted out of ore then hammered into
shape.
© South Tyrol Museum of Archaeology, EURAC, Samadelli, Staschitz
© South Tyrol Museum of Archaeology
Copper isn’t very good for making tools. It’s better than
stone, but it’s too soft; it will bend if it hits another hard object.
Also, because copper is so soft you can’t make big tools out of it.
If you want to make big tools you have to use a lot of copper.
Using that much copper makes the tool too heavy to use and too
expensive to make. Remember, smelting metal is difficult work.
To solve the problem of copper being too soft, people learned
that if you melt copper and tin and mix them together you make
bronze. Scientist and historians call the time period that bronze
was used the Bronze Age.
3
There is one main problem with using bronze to make
tools. The problem is: finding copper is easy; finding tin is hard.
For example, during the Bronze Age in Europe most of the tin was
found in the Cornwall region of Great Britain. If you wanted to
make bronze you had to trade for the tin. This was true if you
were an Egyptian, European, or almost anyone else. There are
really only two places that we know of that had copper and tin
together. So unless you lived in one of those two places, you had
to trade for the tin.
Bronze is much better than copper to work with. For the
first time, large tools, including swords and armor, could be made.
The ancient Egyptians used a crooked bronze sword called a
khopesh. In Europe, the most common type of bronze sword was
a long 20 to 35 inches (50 to 90 cm) leaf-shaped blade. China was
also making bronze swords during the Bronze Age. The Chinese
swords were more complicated than the Mesopotamian and
European swords. They used two different harnesses of bronze
and more complicated blade shapes.
Scientists think the supply of tin became scarce.
Something happened, they’re not sure what, to disrupt the tin
trade routes. It could have been disease, war, or migration. No
matter what the cause, a new metal had to be found. The solution
was iron. Iron was a little easier to work with and much easier to
find. Iron wasn’t as good as bronze but it was good enough and it
was cheaper. Eventually people learned how to make iron in a
way that it became as good as bronze. Then people learned how
to make steel from iron. Steel is much better than iron or bronze.
4
The use of steel is the foundation of our modern world.
Steel is all around you. It makes the nails and screws that hold up
houses. Without steel we wouldn’t have skyscrapers and modern
cities. Without steel we couldn’t have cars, trucks, buses, trains,
planes, or modern ships. Without steel our modern world would
be very different.
Questions:
1.
What is the main idea of this article? (1 point)
2. Copper is soft but could be made stronger through smelting.
Describe this process. (2 points)
But what about the other metals, do we still use them
today? Yes, of course we do. Copper and gold are still used in
jewelry. It’s copper wire that brings electricity to your house.
Copper and gold form the circuits that allow your computer and
other electronics to work. The pins on your computer’s CPU are
plated in gold. Most houses have copper water pipes.
Bronze is used in bells, sculptures, Olympic medals, and
probably in other places as well. We use metal everywhere. It is in
nearly everything we do. You would have to work really hard not
to use some kind of metal every day. Look around and see just
how much our modern world depends on our precious metal.
3.
What is one problem with making things out of copper? What
was needed to overcome this problem? (2 points)
4.
Why did iron replace copper as the metal of choice for tools? (1
point)