[en] We carried out an interlaboratory comparison in gamaspectrometric determination of the radionuclide activity concentrations in a sample of superficial rocks from the island of Jabuka. Samples in a cylindrical 100 ml geometry and in a 1 l Marinelli beakers were used to measure the activity concentrations of 137Cs, 40K, 226Ra, 228Ra, 238U, 235U, and 210Pb. The rock sample has specific characteristic when compared with samples of water, food, or sediments, which are usually used in intercomparisons, and this consequently affects its use in gammaspectrometry. Therefore, we especially paid attention to sample preparation. The material was homogenised by grinding in a geological mill down to the grain size of 2 mm, and subsequently it rested in order to obtain equilibrium of naturally occurring radionuclides. In addition to exhibiting enhanced natural radioactivity, this sample was special by its high density which significantly influenced the attenuation of gamma radiation, hence imposing the necessity of correcting measured activity concentrations. These corrections were especially important at low energies (below 100 keV), i.e., for gamma rays emitted by 210Pb and 234Th.(author)