Assessment of gamma-ray emissions from natural and manmade decorative stones

Decorative stones (32 natural and 18 manufactured) and five ceramic tiles that are used in home interiors were measured with gamma-ray spectrometry, to identify and quantify the naturally occurring radionuclides. Activity concentrations of the radioisotopes varied by more than two orders of magnitude across the stone samples, with maximal levels of 3380, 850, and 2130 Bq/kg, for ²³⁸U, ²³²Th, and ⁴⁰K, respectively. A radiation index and measurements with a radiation meter established that the annual effective dose rates due to a 1 h/day exposure to gamma rays emitted by the granite samples were often low, but can occur as high as 1 mSv/year.