The area appears to be underlain by Juro-Cretaceous Coast Plutonic Complex quartz monzonite. The Baveno is comprised of a coarse-grained biotite granite. Compositionally, the orthoclase is a rich pink colour and is more abundant than plagioclase. The plagioclase ranges from albite to oligoclase in composition and is greyish-white. In thin section the orthoclase is very turbid due to kaolinization, while the plagioclase, which is much fresher, is partially altered to sericite and epidote. The biotite is generally altered to a chlorite which polarizes in a deep blue colour, the chloritization having been associated by the separation of a little secondary magnetite. Quartz is abundant with minor micrographic intergrowths with orthoclase. Crystals of sphene, a few of which are visible to the naked eye, are relatively abundant, usually approximating their habitual wedge-shaped outlines. A few grains of epidote, some of which are so distinctly pleochroic, approach allanite in composition. Two small crystals of zircon, a few short needle-like prisms of apatite and a small grain of pyrite were also observed in thin section.