Igneous rocks are formed from magma.

8.2 Igneous rocks Big crystals or small? Magma cools more quickly on the surface to make rocks with smaller crystals. These are extrusive igneous rocks. Magma cools slowly underground to form rocks with big crystals. These are intrusive igneous rocks. Captions: <Magma cools slowly underground to make rocks with big crystals. These are intrusive rocks.> <Magma cools more quickly on the surface to make rocks with smaller crystals. These are extrusive rocks.>

Rocks are a mixture of minerals. 8.2 Igneous rocks Rocks are a mixture of minerals. Minerals are elements or compounds that occur naturally in the Earth. They usually have a crystal structure. Rocks are made up of a number of minerals.

Rocks are a mixture of minerals. 8.2 Igneous rocks Rocks are a mixture of minerals. Caption: <This granite is a mixture of 4 minerals: quartz (grey crystals, calcium feldspar (white crystals), biotite (black crystals) and potassium feldspar (pink crystals).>

Most igneous rocks are… …hard and strong

…and non-porous (water doesn’t soak into them) 8.2 Igneous rocks …and non-porous (water doesn’t soak into them)

Granite is hard, strong and non-porous 8.2 Igneous rocks Granite is hard, strong and non-porous That’s why it makes great kerbstones… … and kitchen worktops

Basalt was formed when magma cooled quickly, say under the sea. 8.2 Igneous rocks Basalt was formed when magma cooled quickly, say under the sea. So basalt has small crystals – you need a hand lens to see them.