Rock of the Month

In celebration of Geodiversity Day 2022, GeoBus launched their very special campaign #RockOfTheMonth!

Each month we learn about a different rock type; its appearance, formation, uses and where you might see an example in the British Isles.

Catch up on each rock type that has featured below and follow us on social media to see future posts on rocks, minerals and fossils!


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Rock name: Obsidian

Rock type: Igneous

Description: Very shiny, with the appearance of natural glass.

Formation: Formed by the very fast cooling of lava.

Uses: Used for a variety of tools during the Stone Age and even now for scalpels in surgery!

Where can I see it?: Whilst obsidian does not occur in the British Isles, pitchstone, a similar rock, occurs on the Isle of Arran and the Sgùrr of Eigg.

Fun Fact: You might have come across the rock name obsidian whilst playing Minecraft!


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Rock name: Conglomerate

Rock type: Sedimentary

Description: Immature clastic rock with a variety of clasts in a range of sizes.

Formation: Formed when large clasts, pebbles or cobbles are transported & deposited in a river system, with finer grained material filling the spaces in between.

Uses: Can be crushed to make an aggregate, which helps make concrete more compact.

Where can I see it?: A great place to spot conglomerate is Dunnottar Castle, Stonehaven.

Fun Fact: Closely related to sandstone, displaying similar sedimentary structures.


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Rock name: Slate

Rock type: Metamorphic

Description: Slate is a fine-grained, foliated rock.

Formation: Formed through the metamorphism of mud stone or shale.

Uses: Often used for roofing, floors and chalk boards.

Where can I see it?: Simply check out the roofs in your local area to see slate in use!

Fun Fact: The colour of slate can be determined by how much iron it contains.


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Rock name: Granite

Rock type: Igneous

Description: Course-grained, intrusive, silica-rich and one of the main components of the Earth’s continental crust. It varies in colour and can be pink to grey.

Formation: Formed below ground over millions of years, allowing the crystals to grow.

Uses: Often used for building walls and as counter tops.

Where can I see it?: You can see many granite buildings in Aberdeen, sometimes referred to as the granite city!

Fun Fact: Some of the oldest igneous rocks in the world are granitic.


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Rock name: Sandstone

Rock type: Sedimentary

Description: Mature sedimentary rock, mostly made up of quartz and varying in colour from grey to red.

Formation: Formed when many layers of sand are compressed together over a period of time.

Uses: Used for buildings across Scotland, including the National Museum of Scotland.

Where can I see it?: A great spot to see red sandstone is at the cliffs along the east coast of Scotland, between Arbroath and Auchmithie.

Fun Fact: A lot of new red sandstone in Scotland was formed during the Permian, when it was laid down as giant sand dunes.


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Rock name: Marble

Rock type: Metamorphic

Description: A very hard rock that polishes well, is smooth in texture and is often white and green in colour.

Formation: Formed when limestone is heated and compressed (metamorphosed).

Uses: Used for worktops, ornaments, and statues.

Where can I see it?: Iona, the Inner Hebrides.

Fun Fact: Glasgow City Chambers has the largest marble staircase in the world!


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Rock name: Limestone, with fossils

Rock type: Sedimentary

Description: A grey, yellow, or white coloured rock, mainly made of calcium carbonate.

Formation: Made from layers of the remains of shells and other sea creatures such as coral.

Uses: Limestone has many uses, including in the construction of buildings and as soil conditioner.

Where can I see it?: You can see limestone at lots of locations across the British Isles, with Malham Cove in England a very famous spot.

Fun Fact: Scottish limestone was once formed when Scotland was positioned in the tropics, closer to the equator.


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Rock name: Basalt

Rock type: Igneous

Description: A dark coloured, fine-grained, extrusive rock (igneous rock produced when molten rock cools at or near the Earth’s surface).

Formation: Formed by the quick cooling of runny molten rock from a volcanic eruption, rich in magnesium and iron.

Uses: Used in construction as building blocks and for making cobblestones and statues.

Where can I see it?: There are lots of excellent examples of basalts in Scotland, including Fingal’s Cave and Castle Hill (a basaltic volcanic plug) in Edinburgh.

Fun Fact: When you look at the moon, the dark sections (known as maria) and many of the volcanoes found on Mars and Venus are made of basalt.


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Rock name: Gneiss

Rock type: Metamorphic

Description: Stripey, with bands of white/lighter and black/darker material with different compositions.

Formation: Formed when rocks are heated and compressed (metamorphosed) a lot!

Uses: Often used in construction, as flooring, for ornaments and as gravestones.

Where can I see it?: The Lewisian Gneiss (the oldest rocks in the UK at 3 billion years old!) can be found in the North West Highlands of Scotland.

Fun Fact: The oldest rocks in the world (4 billion years old) are gneiss, found in Canada.


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Rock name: Diorite

Rock type: Igneous

Description: Speckled white, grey and black rock, with a “salt and pepper” appearance, sometimes described as white granite.

Formation: Formed when a moderately silica-rich, less runny magma cools slowly underground over a long time.

Uses: A base material in the construction of roads, buildings and car parks. It is also used to help control erosion.

Where can I see it?: The Highlands, the Lake District and Snowdonia.

Fun Fact: Diorite was popular among ancient sculptors of the Middle East. The Code of Hammurabi is a black diorite pillar, seven feet tall, inscribed with Babylonian laws in 1750 BC.


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Rock name: Coal

Rock type: Sedimentary

Description: An organic sedimentary rock that is black in colour, with a slight sheen. Most types are relatively lightweight.

Formation: Coal is a fossil fuel. Plants and other organic matter die and form layers in swamps and forests. After compression, heating and lots of time, coal forms.

Uses: Coal is burned to generate electricity and is also used in the production of chemicals.

Where can I see it?: Yorkshire, East Scotland (Carboniferous Fife) and Cumbria.

Fun Fact: A third of the US electricity production is sourced from burning coal.

Mica schist

Mica Schist

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Rock name: Mica schist

Rock type: Metamorphic

Description: Shiny and silvery, with the flat surfaces of mica crystals sparkling in the light.

Formation: Formed when basalt, shale or mudstone are put under great pressure and heat (metamorphosis). The thin flaky mica crystals all align in the same directions (foliation).

Uses: Micas are used in products such as drywalls, paints, and electronics. The mineral is often used in cosmetics to create shimmer.

Where can I see it?: The Highlands, for example Loch Eilt.

Fun Fact: Schist is found in the basement rocks of Mount Everest. The German word for mica is “glimmer”.

Curriculum Links
  • Having explored the substances that make up Earth’s surface, I can compare some of their characteristics and uses.  SCN 2-17a
  • Having investigated processes which form and shape landscapes, I can explain their impact on selected landscapes in Scotland, Europe and beyond.  SOC 3-07a
  • National 5 Environmental Science –
    • Geosphere Definitions: weathering, transportation, erosion, deposition, igneous, sedimentary, metamorphic, rock, mineral, ore, porosity, permeability.
    • Structure of the Earth
    • Rock cycle processes
    • Relationships between rocks, minerals and ores
    • Properties of rocks
    • Limestone

Is there a rock type you would like to know more about?! Send your rock type requests to [email protected]!