//Pre-Cambrian rock

Pre-Cambrian rock

Formed before plants evolved

On your right are Coedana Granite rocks from Anglesey – they are very very very very old.

The granite was formed 615 million years ago when hot, liquid magma was forced into the centre of rocks created 1.8 billion years ago. Later,  the granite was crushed and altered during periods of earth-movements

This hard rock is an intergrowth of sparkling crystals of quartz, mica, and feldspar. The black lines are cracks which were filled with black crystals.

Good for plants

Pre-Cambrian granites create fairly acid soils that are full of nutrients, ideal for plants such as Anglesey’s county flower, the spotted rockrose Tuberaria guttata.

The rocks’ rough surface is good for lichens too – over 25 lichen species have colonised these rocks.

One of them may have annoyed you – it’s resistant to pollution, grows on concrete pavements and looks like its name, the chewing gum lichen Lecanora muralis.

origin of the pre-cambrian rocks at the NBGWhere do these granites come from?
Gwalchmai Quarry in Anglesey


Pre-Cambrian Rock display at the NBG

Feldspar and mica crystals
Feldspar and mica crystals

'Chewing-gum' lichens
‘Chewing-gum’ lichens

Spotted rockrose
Spotted rockrose