Single phase pure SiO2, exhibits a strong and symmetric X-ray fluorescence (XRF) peak at 1.741 keV, which does not depend much on the size of the particles. Moreover, the separated particles of 30-110 mu m size strongly interact with 5-20 wt % WO3 additions of similar particle sizes, and show dramatic changes of peak intensity (I-p), half-bandwidth 2 Delta theta(1/2), (i.e. the full width at the ha If peak-intensity), and integrated intensity (I) of the signal as a function of size of the particles. The WO3, fluoresces at the relatively higher energy of 8.39 keV with adversely modified intensity I-p or I in such a peculiar way that the total intensity I-t in the two signals of the two WO3 and SiO2 phases is nearly constant. The results are tested and applied to XRF analyses of a wolframite ore having SiO2 and WO3 as the two major phases. In all these examples, the intensities of the SiO2 and WO3 signals vary, basically due to the expected macroscopic electromagnetic interactions between the two phases.