In this Natural Monument of Pedras Ruivas, a pegmatite with spodumene emerges that is characterized as a mineral of interest due to its chemical composition (lithium presence) and its application as a kinematic deformation marker. The distribution pattern of this and other aplite-pegmatite bodies is strongly conditioned by the stress fields of the Varisca deformation phases, by the structuration they determine in the host-rocks, and by the interference of the Varisca deformation in the steps of ascent and installation of the granitic massifs. The tangential kinematics is decisive in the implantation mode.