Between Perranporth and St Agnes lies Cligga Head, inside of which lies some of the most complicated geology of the West Country. Although some of the Polzeath slate cliffs further North run them close, these are the most colourful cliffs in Cornwall. These are a mixture of fine grained rhyolite, medium grained granite and coarse grained pegmatite, altered to greisen, and surrounded by killas (Devonian clay slates).
This area has, as might well be imagined, been extensively mined, for casseterite, from which tin is extracted, and wolframite, from which tungsten is extracted. Lesser amounts of arsenical pyrite, chalcopyite and bornite (both containing copper), and silver ore are also present.
The eagle eyed will spot a substantial area of turquoise copper staining on the cliffs too. The presence of these minerals adds to the beautiful sea colour here (very visible on the google map too).
Old mine entrances to the lower levels can be seen at the base of the cliff, accessible from an allegedly scary path that descends from the top of the cliff, and the top of the cliff is covered in the ruins of old mine buildings and the dressing levels. The cliffs themselves are party eroded from natural causes but have also experienced several collapses due to the mining activity.
Cligga Head is a fascinating area that I would like to revisit to explore the beach level mine entrances (assuming I can get down the path!).