A technique for experimental determination of concentrations and distribution of trace elements is described. The technique employs nuclear emulsions to register β particles from spontaneous decay of a radioactive isotope. At least 58 elements in the periodic system can be studied experimentally in this way. A detailed description of the technique using carbon 14 and samarium 151 as examples in ?10-mg experimental charges is provided. An assessment of analytical uncertainties and tabulations of corrections for 21 common minerals are also presented. It is shown that an accuracy of better than 5% can be attained for element concentrations less than 1 ppb. The data from carbon 14 and samarium 151 are used in calculation of sensitivities and consideration of analytical problems for 21 commonly used trace elements.