 The changes to sedimentary deposits due to intense pressure and temperature effects have given rise to metamorphic rocks such as schist, gneiss & the economically important marble.Granite outcrops can also be found relatively close (10 km) to Caunes adding complexity to the geology.It is expected that groundwater percolating though the acidic granite provides much of the soft water to the l’Argent Double in an area where hard water is more usual.