In regard to the plains of the east coast of Corsica, as the plains Biguglia, Mariana, and Aleria, they are diluvial deposits of the period when the floods destroyed vast numbers of animal species. Among the diluvial fossils in the neighbourhood of Bastia, the head of a lagomys has been found—a small hare without tail, existing at the present day in Siberia.
There is no volcano in Corsica; but traces of extinct volcanoes may be seen near Porto Vecchio, Aleria, Balistro, San Manza, and at other points.
It seems almost incredible that an island like Corsica, so close to Sardinia and Tuscany, and, above all, so near the iron island of Elba, should be so poor in metals as it really is. Numerous indications of metallic veins are, it is true, to be found everywhere, now of iron or copper, now of lead, antimony, manganese, quicksilver, cobalt, gold and silver, but these, as the engineer Gueymard has shown in his work on the geology and mineralogy of Corsica, are illusory.
The only metal mines of importance that can be wrought, are, at present, the iron mines of Olmeta and Farinole in Cape Corso, an iron mine near Venzolasca, the copper mine of Linguizzetta, the antimony mine of Ersa in Cape Corso, and the manganese mine near Alesani.
On the other hand, Corsica is an inexhaustible treasury of the rarest and most valuable stones, an elysium of the geologist. But they lie unused; no one digs the treasure.
It may not be out of place here to give a detail of these beautiful stones, arranged in the usual geological order.
1. Granites.—Red granite, resembling the Oriental granite, between Orto and the lake of Ereno; coral-red granite at Olmiccia; rose-red granite at Cargese; red granite, tending to purple, at Aitone; rosy granite of Carbuccia; rosy granite of Porto; rose-red granite at Algajola; granite with garnets (the bigness of a nut) at Vizzavona.
2. Porphyries.—Variegated porphyry in Niolo; black porphyry with rosy spots at Porto Vecchio; pale yellow porphyry, with rosy felspar at Porto Vecchio; grayish green porphyry, with amethyst, on the Restonica.
3. Serpentines.—Green, very hard serpentines; also transparent serpentines at Corte, Matra, and Bastia.
4. Eurites, amphibolites, and euphotides; globular eurite at Curso and Girolata, in Niolo, and elsewhere; globular amphibolite, commonly termed orbicular granite (the nodules consist of felspar and amphiboles in concentric layers) in isolated blocks at Sollucaro, on the Taravo, in the valley of Campolaggio and elsewhere; amphibolite, with crystals of black hornblende in white felspar at Olmeto, Levie, and Mela; euphotides, called also Verde of Corsica, and Verde d'Orezza, in the bed of the Fiumalto, and in the valley of Bevinco.