[en] It is shown that within the igneous rocks the granites have the highest uranium and thorium contents. These elements are extractable from the rock by means of leaching or chlorination. The energy needed for the extraction is less than 10% of the energy obtainable by burning the uranium and thorium in breeder reactors. In order to increase the economy of the uranium and thorium extraction, other metals (Si, Al,..) are suggested to be extracted from the granite. The reserves of energy contained in the uranium and thorium of the granites make it possible to meet the needs of energy of a future world population of 8 to 12 billions requiring 15 kW per capita for thousands of years