English: These mountains are located on the southern margin of the vast Canigó-Carança massif, on the France-Spain frontier, above the Vallter 2000 ski station. Here, the main geological formation is composed of orthogneiss, or metagranite. This formation is derived from the granite of a deep igneous intrusion which, around 470 million years ago, in the Ordovician period, was intruded into sedimentary formations of Cambrian and older ages. During the Hercynian orogeny, around 300 million years ago, the granite was metamorphosed into gneiss. It has since been uplifted by tectonic forces and exposed at the surface by erosion.

A particular geological feature of this sector of the massif is the existence of a number of "giant quartz veins" that cut through the gneiss in a west-east direction. These quartz veins are the largest of their kind in the Pyrenees.

See: B. Laumonier et al., Notice explicative de la feuille Prats-de-Mollo-La-preste (1099) à 1/50 000; http://ficheinfoterre.brgm.fr/Notices/1099N.pdf.
E. Deloule et al., In-situ U–Pb zircon ages for Early Ordovician magmatism in the eastern Pyrenees, France: the Canigou orthogneisses; www.researchgate.net/publication/225899588.

Eloi González-Esvertit et al., Compiling regional structures in geological databases: The giant quartz veins of the Pyrenees as a case study; https://www.sciencedirect.com/science/article/pii/S0191814122001973.