An on-line X-ray fluorescent monitoring system uses a probe having an X-ray transmitter and a fluorescent X-ray detector placed adjacent a recessed chamber in a coal feed line having an X-ray transparent window. Pulverized coal traveling through the coal feed line collects in the recessed chamber and rests against the X-ray transparent window where it is bombarded by excitation X-rays from the transmitter. The probe receives fluorescence from the X-ray excited coal and transmits the data to a data acquisition and control means for analysis and use. A pressurized air tube is provided at the base of the recessed chamber for blowing accumulated pulverized coal out of the recessed chamber and back into the feed line, thereby allowing a new sample portion of pulverized coal to settle into the recessed chamber for analysis. The on-line analyzer can also be used to determine concentrations of other elements of interest in the pulverized coal, such as iron, chlorine, etc.