From a geological point of view, Portugal is a diverse and complex Country, with potential in various mineral and non-mineral resources.
Alentejo is occupied by Ossa-Morena Zone, which is an extremely complex and diverse unit that begins with a poly-metamorphic Precambrian, followed by Cambrian and Silurian formations, and ends with a flysch sequence from the late Devonian period.
Relative to non-metallic minerals, this geo-tectonic unit is rich in ornamental rocks, particularly marble, like the Estremoz-Borba-Vila Viçosa anticline, as well as granites like in the Portalegre district.
The NE sector has a predominance of granitic rocks ("calcalkali", porphyritic, biotitic).
In the south, the basic character of the intrusions gradually increases, with "calcalkali" becoming predominant: gabbro, diorites, serpentinites and anorthosites (Beja ophiolite complex), various different porphyries, and later intrusions comprising gabbrodiorites, granodiorites, tonalites and granites (Évora Massif).