In Petralia Sottana, in Raffo Fraction,is located the one of Europe richest salt deposits, enclosed in a salt lens inside the heart of the mountain at 1100 meters above sea level.

The salt field, 250 meters thick and 2 km² large, contains salt with a purity of sodium chloride equal to 99.9%.

It is assumed that, due to its location and exceptional purity, it is a secondary origin salt deposit, which is a deposit pre-existing to the island geological upheavals which dissolved and recrystallized the first formation salts.