Everyday Uses of Rocks and Minerals - Shelf 8
It's hard not to experience iron and aluminum in our everyday lives. Iron ores are usually compounds of iron and oxygen, otherwise known as rust. Much of these ores were formed when the earliest photosynthesizing microbes began to pump oxygen into the earth's oceans. In a way, iron ores are fossils, so all iron and steel we use are made from fossils. Iron is commonly used in different compound with carbon and silicon. Different ratios of the other elements determine its physical properties, which vary between cast iron, as in the frying pan, and steel, as in the reusable coffee cup.
Aluminum is found naturally as bauxite, made of aluminum bonded with water. Purifying bauxite used to be expensive and slow, so aluminum was a rare and valuable metal in the 18th and 19th centuries. That's why the top of the Washington monument was covered in aluminum -- it was like covering it in silver! Since the late 1880s, aluminum ore has been purified using electricity, and it has become cheap and plentiful. Benjamin Franklin would think we all live like kings if he knew that we casually drink out of aluminum cans and use aluminum foil to save our leftovers.