Green Geology

How to get there:

Rail or bus

 

Nearest railway station:

Roche

 

Accessibility:

Uneven path, stile, steps.  Ladder up to the chapel.

Permian

 

Site of Special Scientific Interest (SSSI)

Roche Rock, Cornwall

Text and photographs:  Naomi Stevenson

 

Page updated July 2014

In the right weather conditions, Roche Rock - which is situated in the middle of a field in the eponymous village of Roche - is a truly brooding landmark.  It is topped by the ruins of a chapel dating back to 1409, dedicated to St. Michael.

 

This is an internationally-famous tor composed almost entirely of light-coloured quartz and black tourmaline – the latter displays a variety of forms here including dense, easily-eroded “pods.”  It is arguably the best exposure of this composition in the country.  The mineralisation very probably occurred ~270 million years ago during the intrusive activity that was then taking place following the Variscan Orogeny.

 

There has been some debate about its origin; it may have formed from a boron/fluorine fluid as a result of magmatic or hydrothermal processes.  It was formed close to the roof of the St Austell intrusion of the Cornubian batholith, which is the granite mass underlying large parts of Devon and Cornwall – it is only 500 m away from the northern margin.  The china clay waste (from the industrial extraction of the products of weathered granite) shows this visibly - stepped waste heaps can be seen from Roche Rock.

 

There is an interpretation board with more information about the site at the entrance to the field it stands in.

Click to enlarge

Click to enlarge

Three outcrops