igneous rocks

igneous rocks form when magma cools and becomes solid

• magma moves up a line of weaknesses in the rock

• intrusive igneous rock - magma that displaces rock inside the crust

• extrusive igneous rock - magma that flows onto the surface (lava)

igneous rocks are massive which means that form one large mass (no layers)

• igneous rocks are crystalline

• consist of many elements e.g. silica, iron and magnesium

• when magma cools elements combine to form crystals and minerals

• magma that cools quickly forms small crystals e.g. basalt

• magma that cools slowly forms large crystals e.g. granite

• contain valuable metals e.g. copper, gold, iron and manganese

• mining companies will mine the metals if it is economical

• used for building materials

• stone chips used to reinforce cement are extracted from quarries

• work surfaces and gravestones are made from granite