The oldest rocks exposed in Caramoan Peninsula are mainly metamorphosed sedimentary and volcanic rocks of unknown age. These are believed to have been subjected to orogeny during the Paleogene. They are overlain unconformably by definitely Cretaceous to Quaternary strata. The metamorphic rocks, together with the Cretaceous and Paleocene strata are intruded locally by ultramafic rocks and diorite. The intrusions are related to major structures. The most prominent structural features are thrust faults, transcurrent faults and broad folds.

The occurrence of iron, manganese, chromite, nickel, copper-lead—zinc, cupriferous pyrite, silver, siliceous clay, sulphur, pyrite, guano, phosphatic rock, marble, limestone, and sand and gravel deposits were confirmed and mapped. However, a great deal of detailed work has yet to be done to ascertain their economic significance.