The paper describes a spectrometric method and apparatus developed for lithology logging in brown coal formations. The nuclear spectromet- ric technique developed is able to delineate coal/sand/clay seams. One requirement was to log inside drilling rods, as well as cased or open holes._x000D_
The method described is based on combined natural gamma and gamma- gamma techniques using a spectrometric system for signal acquisition and subsequent computer based on-line data analysis and interpretation.