The geology of Cornwall

The Lizard: Serpentine and an Ancient Ocean Floor

At the southern tip of Cornwall lies one of Britain's most unusual geological landscapes. The Lizard is famous for its serpentine-rich rocks, dramatic coastal exposures and distinctive heathland.

These rocks began deep beneath an ancient ocean. Geological forces later brought them to the surface, where they now provide a remarkable window into the Earth's oceanic crust and upper mantle.

Kynance Cove on The Lizard Peninsula, with rocky islets and a sheltered beach — Kynance Cove, photographed by Dr Neil Clifton. Licensed under CC BY-SA 2.0. Image source.

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By Martin Frost · Updated 13 October 2026

A very different geology

Much of Cornwall is associated with granite, slate and sedimentary rocks. The Lizard is different. Its geology includes serpentinite, gabbro, basaltic rocks and metamorphic rocks such as schist and gneiss.

Together, these rocks form part of what geologists call the Lizard Complex. They represent fragments of ancient oceanic lithosphere — the rigid outer part of the Earth that includes the oceanic crust and uppermost mantle.

The rocks formed in an oceanic setting during the Early Devonian, around 400 million years ago, at a spreading ridge in an ocean that lay to the south of what is now Britain. During later plate movements associated with the Variscan mountain-building event, pieces of this oceanic material were pushed over continental rocks and incorporated into the geology of south-west England. Geologists call a slice of ocean floor emplaced on land in this way an ophiolite, and the Lizard is the best-known example in Britain. Its northern edge is marked by the Lizard Boundary Fault, which separates it from the Devonian slates of the rest of Cornwall.

Why The Lizard matters

Oceanic mantle rocks are normally hidden beneath the Earth's crust. The Lizard preserves an unusually accessible example of these rocks at the surface, making the peninsula important for understanding plate tectonics and the evolution of the Earth's crust.

What is serpentine?

The word serpentine is commonly used for the distinctive green, red and dark-coloured rock found around The Lizard. More precisely, the rock is generally called serpentinite, while serpentine refers to a group of minerals that form a major part of it.

The original rocks were rich in minerals such as olivine and pyroxene, which are characteristic of the Earth's mantle. When these rocks interacted with water, chemical reactions altered some of their original minerals and formed serpentine-group minerals. This process is known as serpentinisation.

The resulting rock can display attractive green, grey, black and reddish colours, sometimes with intricate veins and mottled patterns. Its appearance has made serpentine valued as a decorative stone and used historically in local craftwork.

Rocky cliffs and boulders at Kynance Cove on The Lizard — Cliffs and rocks at Kynance Cove, photographed by Kolforn. Licensed under CC BY-SA 4.0. Image source.

The geological map of The Lizard

The peninsula contains several related but distinct rock units. Serpentinite is particularly associated with the mantle-derived rocks, while gabbro and other igneous rocks represent different parts of the ancient oceanic system. Metamorphic rocks record the effects of heat, pressure and deformation.

The simplified map below illustrates the distribution of the main geological units. The green peridotite and serpentinite covers much of the centre of the peninsula, around Goonhilly Downs; the Crousa gabbro lies in the east near Coverack; and the schists of the Old Lizard Head Series form the cliffs around Lizard Point. The red line is the Lizard Boundary Fault. Boundaries in a simplified map should be treated as an overview rather than a substitute for detailed geological mapping.

Simplified geological map showing the main rock units of The Lizard Peninsula — Simplified geological map of The Lizard by Andy F. Released into the public domain. Map source.

Kynance Cove: geology on the coast

Kynance Cove is one of the best-known places to appreciate the rocky landscape of The Lizard. Offshore islets, steep-sided rock faces and boulders create a dramatic setting, with the colours of the rocks contrasting with the sea and pale sand.

The coast exposes parts of the Lizard Complex and shows how resistant rock masses, fractures and coastal erosion interact. Waves exploit weaknesses in the rock, gradually widening cracks and helping to form small coves, clefts and isolated stacks.

The coastal landscape is constantly affected by wave action and weathering. Some rock surfaces can be slippery, and access to the beach depends on tides and conditions. Check local access information before visiting and avoid climbing unstable or exposed rock faces.

Coverack: where the mantle meets the crust

On the east coast, the shore at Coverack is one of the few places in Britain where the boundary between mantle rocks (serpentinite) and the overlying ocean crust (gabbro) – the ancient “Moho” – can be walked across. Look for the change from smooth, greenish serpentinite to the coarser, speckled gabbro.

Geology and unusual plants

The importance of The Lizard's geology extends beyond its rocks. Serpentinite-derived soils tend to have high levels of magnesium and iron and relatively low levels of several nutrients, including calcium. Their chemistry creates challenging conditions for many plants.

The result is a distinctive mixture of heathland and grassland vegetation. The peninsula is particularly well known for Cornish heath, which in Britain grows wild almost only on the Lizard, alongside a range of specialised plants and species that are uncommon elsewhere in Britain. English Nature also noted coastal plants such as thrift and sea campion growing well inland here, reflecting the chemistry of the serpentine soils.

The relationship between geology and biodiversity is one reason the area is important for nature conservation: much of the peninsula is a National Nature Reserve, with more than 250 species of national or international importance. The combination of unusual rocks, local soils, coastal exposure and a mild maritime climate creates habitats with considerable botanical interest.

The Lizard landscape

Coastal landscape on The Lizard Peninsula in Cornwall — The Lizard, photographed by Richard Dunn. Licensed under CC BY-SA 2.0. Image source.

The Lizard is the southernmost part of mainland Britain, and Lizard Point is its most southerly tip. Its gently rolling plateau, open heathland, rocky coves and exposed headlands reflect the combined influence of its unusual geology, long-term erosion and maritime climate.

Exploring the peninsula provides an opportunity to see how geology shapes not only the physical landscape but also the soils, vegetation and character of a place.

The Lizard geology at a glance

Key rock: Serpentinite
Other rocks: Gabbro, basaltic rocks, schist and gneiss
Original setting: Ancient oceanic lithosphere
Approximate age: about 400 million years (Early Devonian)
Type of complex: Ophiolite – ancient ocean floor on land
Key process: Serpentinisation
Famous location: Kynance Cove

What to look for

Green, red and dark-coloured serpentinite
Veins and fractures in exposed rocks
Rocky islets and coastal outcrops
Heathland growing on unusual soils

Where to see the rocks

Kynance Cove – serpentine stacks and islets
Mullion Cove – serpentine cliffs and harbour
Cadgwith Cove – fishing cove on the east coast
Kennack Sands – serpentine and Kennack gneiss
Coverack – gabbro and the ancient Moho
All Lizard beaches

Explore more Cornwall geology

Discover other geological landscapes around Cornwall.

Geology of Cornwall Bodmin Moor Bude & the Culm Coast Meadfoot Beds

Visiting the coast

Check tide times and weather forecasts before exploring coves and rocky shores. Keep clear of unstable cliffs, and follow local access signs and conservation guidance.

The Lizard Geology FAQ

What is the Lizard made of?

The Lizard is built from the Lizard Complex – serpentinite (altered mantle rock), gabbro, basaltic dykes and lavas, and metamorphic schists and gneisses. Together they are a slice of ancient ocean floor and upper mantle, known to geologists as an ophiolite. This is quite different from the slate and granite found across the rest of Cornwall.

How old are the Lizard rocks?

The oceanic rocks of the Lizard formed around 400 million years ago, in the Early Devonian, at a spreading ridge beneath an ocean that lay to the south of what is now Britain. They were later pushed onto the edge of the continent during the Variscan mountain-building episode.

How did ocean-floor rocks end up on land?

Normally ocean floor sinks back into the Earth when plates collide. During the Variscan collision a slab of the Lizard ocean floor was instead thrust up and over the continental rocks to the north – a process called obduction. The Lizard Boundary Fault, crossing the peninsula from the west coast north of Mullion to Porthallow on the east coast, marks the base of the thrust slice.

What is the difference between serpentine and serpentinite?

Serpentine is the name of a group of green minerals. Serpentinite is the rock made mostly of those minerals, formed when mantle rock rich in olivine and pyroxene reacts with water. Locally the rock is simply called ‘serpentine’, and it has been carved and polished into ornaments on the Lizard since the 19th century.

Where can I see the serpentine on the Lizard?

Kynance Cove is the best-known place, with green and red serpentine stacks, islets and boulders. Serpentine can also be seen at Mullion Cove, around Lizard Point and at Cadgwith. On the east coast, Coverack shows gabbro and the boundary between the mantle and the ocean crust.

Why does Cornish heath grow on the Lizard?

Soils formed from serpentinite are rich in magnesium and iron but low in calcium and other nutrients, which few plants tolerate. Cornish heath is one of the specialists that thrives on them, and in Britain it grows wild almost only on the Lizard. The peninsula is a National Nature Reserve, with over 250 species of national or international importance.

Is the Lizard the most southerly point in Britain?

Lizard Point is the most southerly point of mainland Britain. The cliffs around it are made of the Old Lizard Head Series – metamorphic schists that are among the oldest rocks on the peninsula.

Can I collect serpentine from the beaches?

Please don’t take rocks from the beaches or cliffs. Much of the coast is protected and owned by the National Trust, and many of the best geological sites are Sites of Special Scientific Interest. Serpentine ornaments made by local craftspeople can be bought on the Lizard instead.