The eclogites, rocks present mainly in the area of Vara, have a very dark coloring, but at close distance, we can recognize the dark red of garnet and the purple of the Rutile inside the matrix of dark green pyroxene.
These rocks are due to very high metamorphism pressure ( 8-10 kbar = about 30-50 km ) and low temperature ( 470° C). Previous set of basaltic rocks. The eclogites can be called even “metabasite” ( metamorphic basalt ) in eclogite facies ( high pressure ASSA temperature).
In Beigua Geopark, several sites of petrography interest present also mineralogical or geomorphological significant features, such as the conspicuous metarodingite dikes (Vara, Bc. Dell’Uomo morto) or the Mt. Tariné block stream. The orogenic built-up resulted in the exhumation and partial re-equilibration (e.g. antigorite olivine in the serpentineschists) of the high-pressure units (Bric dell’Uomo Morto). The subsequent orogenic collapse produced post-orogenic tectonic breccias and was related to the erosion of the structural higher and deepest-in-the subduction units.
The garnets are very abbundant in the eclogites, especially in the Vara area where, along the Torrent Orba, some interesting outcrops are likely to be found also in the riverbed. An interesting outcrop is located south – west of Piampaludo, by the Orbarina torrent (tributary of the Orba) where the rhombododecahedral garnet crystals have a pinkish colour, are well shaped and characterised by remarkable brightness; they can be found in a very massive eclogitic rock and they are mingled with stretched and interwoven specimens of smaragdite which constitute a green-coloured substratum.
Still in this area, and more precisely along the range separating the Orba Valley from the Orbarina valley, the garnets are contained in brown-reddish rodingite lenses and nodules.
As for the rocks of some economic interest, passed (and to a minor extent, recent) quarry activity was carried out in the Vara valley serpentineschist.