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)