What are rocks made of?

Every type of rock has its own "recipe" of one or more minerals found on Earth, each with its own unique shape and colour. Earth's rocks are like buried treasure - they are full of valuable minerals and contain metals, gemstones, fossils, and fuels, such as coal and gas.

Fast Facts about Rocks

1. Earth started as a fiery mass of molten rock, but about 4 billion years ago the outer layer began to cool and form a hard crust.
2. There are many types of rocks, formed in three main ways.
3. Most igneous rocks appear on the surface as melted rock (magma) brought to the Earth's surface by volcanoes. When this cools, it crystallizes into solid rock.
4. Sedimentary rocks are made from loose rocks, and the ancient remains of animals and plants. Carried by wind and water, they compact and harden into solid rock over millions of years.
5. Metamorphic rocks are rocks that change when they are baked and crushed by the heat and pressure deep below the Earth's surface.