The mountain pass Col de Marsolino 10 km south of Calvi offers an instructive panoramic view on the ring dyke. In addition, the roadcut exposes the contact of the ring dyke rhyolite to the surrounding granite country rocks.
The rhyolite in this outcrop has a very light gray color and is fine-grained. It is mainly located in the lower parts of the outcrop. The granite is light gray as well, but individual crystals can be identified. It generally overlies the rhyolite, it is also intruded by rhyolite dykes from below. This cross-cutting relationship clearly indicates the relative ages of the two rocks: The intruding rhyolite must be younger than the intruded granite.