Rock Types Igneous

Igneous Rocks-

Basalt

Characteristics

• microscopic crystals

• black or gray in colour

• very hard (difficult to scratch)

• impermeable (will not let water pass through)

• fine grained in texture

located on the: Giant’s Causeway, County Antrim

Basalt is formed when liquid rock (magma) erupts onto the earths surface as lava. It cools and solidifies rapidly and therefore large crystals are unable to form. This rock is the most common type which makes up the crust of the earth. The rock under all of the world’s oceans is made of basalt.

Granite

Characteristics

• large crystals randomly arranged

• pale in colour

• very hard (difficult to scratch)

• impermeable (will not let water pass through)

located on the: Mourne Mountains, County Down

Granite is formed when magma from the mantle cools underground inside the crust. As it cools very slowly, large crystals form in the rock.