X- or .gamma.-ray scatter assemblies are used in quantitative determination of the concentration of ash in coke or coal. The assemblies each comprise an X- or .gamma.-ray source, an energy sensitive detector to detect X- or .gamma.-rays resulting from scatter in the coal or coke of X- or .gamma.-rays from the source, and shielding means adapted to reduce the intensity of direct X-rays or .gamma.-rays and to collimate partly the beam of X-rays and or .gamma.-rays to ensure maximized matched volumes for all assemblies and deep penetration in the coal. The assemblies are associated with an electronic analyzer adapted to select all or part of the detected X-ray or .gamma.-ray spectrum, thereby modifying the output of the assemblies. Two or more assemblies are employed in an apparatus and method for analyzing coal or coke.