Balmuccia peridotite

In Balmuccia, you can see one of the best-preserved examples of the Earth’s mantle in the world: the famous Balmuccia peridotite.

The main mineral comprising this rock is olivine, with smaller amounts of pyroxene and spinel. Veins rich in green and grey pyroxene, cutting through the light brown peridotite, are easily recognisable. These veins result from the crystallisation of basaltic magmas, which flowed along fractures, formed during very ancient (undatable) episodes of partial mantle melting.

The Earth’s mantle makes up more than 80 per cent of the Earth but, despite its enormous volume, it rarely reaches the surface, as it is covered by the Earth’s crust, which is much less dense. The Balmuccia peridotite was incorporated into deep layers of the continental crust more than 290 million years ago, long before it was brought to the Earth’s surface as a result of the Alpine orogeny.