The Mineralogy Institute of Paris (IMPMC) has shown that all volcanic lavas of the Mont-Dore massif – including the Sancy ridges pictured here – are constituted by two different series of rocks, evenly distributed across the massif. The first series, poor in silica, includes basalts rich in olivine, half-mourning basalts, phonolites, labradorites and ordanchites. The second series, rich in silica, is more exceptional: it includes low-in-olivine basalts, doréites, sancyites and rhyolites.