The outcrop of Pedras Parideiras (rocks delivering stones), geologically called nodular granite of Castanheira, is a unique granitization phenomenon in the world. It is the outcropping granite nodules which are surrounded by a biotite cover (black mica) in the form of a biconvex disc. These nodules are more resistant to weathering agents than the host rock so as soon as the unifying layer wears out, by erosion, the nodules are released and accumulate in the soil, leaving a cavity in the rock whose walls are coated with a biotitic cover. In popular language, the stones “gave birth” to others, hence the name “rock delivering stones”. Its importance is due to the rarity of this worldwide phenomenon and the mysticism given by the people.