Rocks

Rocks

Group

How Formed

Example

Igneous

Cooled down Magma

Granite

Basalt

Sedimentary

Pressed remains of plants and other rocks

Limestone

Sandstone

Metamorphic

Rocks that have been through a ‘Great Change’ of heat or pressure

Quartzite

Marble

Igneous Rocks

Igneous rocks are formed from cooled down magma. Whether the magma cooled down quickly or slowly determines the rock type formed.

Granite

Granite is a hard rock with crystals in it. It was formed when magma cooled slowly. It is hard. It can be multi-coloured. It is used for kitchen worktops and fireplaces. It can be found in the Wicklow Mts.

 Basalt

Basalt is a heavy, black rock. It was formed when magma cooled quickly on the earth’s surface. It is hard. It can be used for road surfaces. It can be found at the Giant’s Causeway.

Basalt at The Giants Causeway by Leanne Mc Glinchey

Sedimentary

Sedimentary rocks get their name from the build up of layers, called strata.

 Sandstone

Sandstone is a soft rock. It varies in colour from yellow to dark brown in colour. It was formed when layers of sand built up in layers. The sand is squeezed (Compressed) together to form a rock. Used for ornamental building and stone walls. Found in the mountains of Munster.

How sandstone is formed by Stephen Mc Elhinney

Limestone

Limestone is Ireland’s most common rock. It is soft and Grey in colour. It was formed by the remains of dead sea creatures building up in layers on sea beds. The layers are known as Bedding planes, these are separated by joints. It may contain fossils. It is Permeable (water can pass through it) and easily worn by acid rain. It can be found in the Burren in Co. Clare. Used for building up roads and for making cement.

A Limestone Pavement by Jordan Tourish

  Metamorphic Rocks

The word Metamorphic means great change. Some rocks are subjected to either a great deal of heat or pressure. This can cause them to change.

 Quartzite

Sandstone changes to quartzite. It is very hard. Sometimes used for roads, Quartz is used in watches. Found in Co. Donegal.

Marble

Marble used to be Limestone. It is also very hard. It has many uses because of its beauty. Fireplaces, trophies etc. It can be found in many colours. Found in Connemara and Kilkenny.

Marble, used for Fireplaces, by Conan Gallagher.

How Rocks are Formed Video

Extracting Rocks

Several methods are used to take rocks out of the ground.

  • Drilling
  • Shaft Mining
  • Quarrying

Drilling

This is used to get oil and gas from deep under the earth’s surface. A deep hole is drilled to get to the oil and it is then pumped to the surface.

Drilling for Oil & Gas by Michael Mc Colgan

Shaft Mining

This method is used for rocks under the surface of the earth E.g. Coal or Gold. A vertical shaft is dug and then horizontal shafts dug across to the rock.

Shaft mining by JP Kelly

Quarrying

Most common form. Used for rock that is on the surface. Explosives are used to break it up then lorries take it away.

Quarrying by Ryan Davis