Pick up a rock. It may look plain. But every rock has a story. Rocks are made of minerals. Minerals are made by nature. They are never alive.

Rocks come in many sizes. A rock can be as small as a pebble. A rock can be as big as a mountain.

Some rocks start as melted rock. Lava is melted rock on the ground. When it cools, it gets hard. Then it is solid rock.

Obsidian is a rock. It is a kind of volcanic glass. Pumice is a rock too. It is full of holes.

Granite is a rock with big crystals. You can see them. They are made of minerals like quartz.

Sandstone is a rock made of sand grains. The grains are stuck together. Rocks like this form in layers, like a stack of pages.

Some limestone comes from sea animals. It is made from their shells and skeletons.

Coal is a rock too. It comes from plants. The plants lived long ago. Some rocks hold the remains of living things.

Wind and rain slowly break big rocks. The pieces get smaller.

Heat and pressure can change limestone into marble. The rock gets a new life.

Lava, sand, shells and plants all make rocks. Every rock has a story. What is the story of the rock in your hand?

Words to know

• granite: rock with crystals
• lava: melted rock
• obsidian: volcano glass
• pumice: holey rock