The earth is made up of several layers from the earth's crust to the core, including magmatic, metamorphic and sedimentary rocks of a multitude of minerals among which we find the radioactive minerals. Thorium and Uranium are spontaneously unstable and continuously transform into other less heavy elements, thus operating a natural transmutation of a less heavy element; the ultimate term of this transformation being Lead, in both cases. This atomic disintegration is accompanied by a particular emission, a more or less penetrating radiation which can be harmful to man and his environment. That it is in the exploration or the exploitation of the radioactive minerals it is not necessary to hide the meanings of protection against the dangers that are present in the sources of radioactive although having applications of energy they numerous; the Governments as well as the Services and Orders of the Geologists of the countries in the process of development must veil to these facts.