This small island sits close to the southern shore of mainland Brittany. Whilst it is easy to imagine that Groix is just a small chip of rock from the mainland it is in fact structured very differently geologically.
Some 300 million years ago two ancient continents joined creating the Super-continent ‘Pangaea’ The Amorican land mass which was very much smaller was caught in between and squashed upwards creating mountainous peaks and folds of metamorphic rock through the softer sedimentary layer, this land mass much weathered and reduced in height now forms North West France. The High pressures acting on the Amorican land mass created a high temperature metamorphosis of the sedimentary rock forming the Granite and limestone rocks of the mainland, Groix however is the result of a low temperature Metamorphosis (subjcted to lower pressures) and as such the rock is far richer in mineral content. There are over 60 different minerals identified in the rock, and has created interest amongst Geologists around the globe. The Southern and Eastern coasts have been designated a Geologic Reserve.
One of the minerals present is Garnet, easy to identify in the rock around Pointe des Chats and it also gives rise to the red sand on the beach ‘Sable rouge’
Taking a tour round Groix is refreshing, from the busy harbour of Port Tudy to the wild and dramatic coastline round the North West point of Pen Men. The South Western part of the coast is open to the full force of the Atlantic swell and contrast sharply to the protected Northern coast.