Pre-Cambrian Rocks

615 million years old

Formed Before Plants Evolved

This 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.

Lecanora muralis

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.

Where do these granites come from? Gwalchmai Quarry in Anglesey