The heterogeneity of trace element distribution in standard rocks poses some problems. Materials of this type are obviously not very useful as standards which are used by analysts to show that a particular analytical method gives satisfactory results. The second difficulty relates specifically to neutron activation analysis. During this investigation it was found that the activated gold can be almost completely extracted from the rock powder with aqua regia. The same was found to be true for lanthanum whereas the extraction of sodium amount to only about 1%. If one takes this observation as evidence for the existence of a specific acid soluble rare earth mineral present in individual particles, it appears possible that results for these elements might be low on account of self-shielding effects.