The structure of Isola Elba is quite complex though the island is not so large (around 210 kmq.) and it can be divided in 5 parts from the geological point of view that in the last millions of years moved for the tectonics so that to be overlapped or tightly connected one with the other.
The first zone includes the area of Punta Calamita and all the coast up to Porto Azzurro and Terra Nera. This part is greatly composed by metamorphic shist, quartz and carbonatic rocks (such as dolomia).
The second zone includes only the area of Terra Nera and Rio Marina and the area inbetween the gulf of Portoferraio and Stella gulf (east of Lacona area). This area is mainly formed by various kinds of schists, marbles, quartzites, and carbonatic rocks.
The third zone is located north-east of Isola Elba and includes the area of Cavo up to Terra Nera. This area is mainly formed by carbonatic rocks, dolomia, schists.
The fourth zone is the largest and includes all the east and central part of Isola Elba, including the south area of Cala Vita, the area inbetween Portoferraio and Capo Stella and the whole area around Monte Capanne. This area is mainly composed by serpentine, gabbros, basalt (typical pillows), carbonatic rocks and schists.
The fifth zone is formed by the west and central part of the island, including the area inbetween Portoferraio, Marina di Campo and Monte Capanne.
These five zones are perfectly and tightly linked one with the others due to the tectonic movements. During these last few millions of years several fractures permitted to fused lavic rocks to reach the surface, creating the oldest granitic rocks of this area, and later to the inner part of Monte Capanne. During the following millions of years erosions and tectonic movements eliminated the coverage of this granitic parts of the island. This event permitted to unhide the granitic soul of Monte Capanne, exactly what we can see nowadays. More on: http://www.italianminerals.com/elba-minerals/geology-of-isola-delba/