why are some rocks radioactive
Radioactive accessory minerals such as zircon may contribute to the radioactivity of a mineral which is otherwise non-radioactive by calculation. Many granites or other igneous rocks contain some radioactivity because of minor, but highly radioactive, accessory minerals.re = mineral density (S Atomic number / Molecular Weight) where re is the electron density in grams/cc.efinition. Radioactivity in minerals are caused by the inclusion of naturally-occurring radioactive elements in the mineral's composition. The degree of radioactivity is dependent on the concentration and isotope present in the mineral.